MAIL EDITION. 
PSICE. 12} CENTS. 
Si jlinu 
THEORY OE POPULATION; 
DEDUCED FROM THE 
GENERAL LAW OE ANIMAL FERTILITY. 
REPUBLISHED FROM THE WESTMINSTER REVIEW, 
FOR APRIL, 1S52, 
SJEftl) an CutvoTiuctfon, 
BY R. T. TRALL, M. I> 
NEW YORK: 
FOWLERS AND WELLS, PUBLISHERS, 
CLINTON HALL, 131 NASSAU STREET. 
Boston, 142 Wasliington-St.] 
[London, No. 142 Strand. A. NEW 
THEORY OF POPULATION; 
DEDUCED FROM THE 
GENERAL LAW OF ANIMAL FERTILITY. 
REPUBLISHED FROM THE WESTMINSTER REVIEW; 
FOR APRIL, 1852. 
8©ft& an Entvotmctfon, 
BY R. T. TRALL, M.D. 
NEW YOREL: 
FOWLERS AND WELLS, PUBLISHERS, 
CLINTON HALL, 131 NASSAU STREET. 
Boeton, l;9 Washington-St] 
1853. 
[London, No. 149 ftrnnd. INTRODUCTION. 
R. T. TRALL, M.D. 
among the many and multiplying problems of this age, none presents a 
more interesting field of research than that of the Theory of Population. 
Slightly and but superficially cultivated hitherto, this subject has appeared 
to us as a deep, dark wilderness, which even the wild spirit of philosophi- 
cal speculation had scarcely penetrated. The world has indeed heard of 
the doctrines of a Malthue; a doctrine which shocks our reason, insults 
the moral sense, and blasphemes Deity, inasmuch as it can provide no bet- 
ter way of keeping the population of the earth down to the level of the 
means of subsistence, than by such “special providences” as war, pesti- 
lence, famine, poverty, intemperance—violence, fraud, crime and want in 
their broadest acceptation! It has heard, too, of the more humane and 
less revolting doctrine of Mr. Doubleday, who contends that “ over-feeding” 
deadens the principle of increase, and that, therefore, the great panacea 
for the evil of too many people in the world is a “ general plethora.” With 
an improved system of agriculture by which the productiveness of the 
earth is to be vastly increased, and excessive alimentation to the extent of 
inducing a certain degree of physiological stupidity and procreative in- 
ability, Mr. Doubleday would have the elements of disorder, so prominent 
and so repugnant in the Malthusian hypothesis, removed from the order of 
Nature. 
But neither system indicates a principle nor points to a law, which, con- 
taining within itself the elements of its own fulfillment, is to govern and 
regulate this matter for all time; and with nothing less than the actual 
demonstration of such a law will the truly philosophical mind be satis- 
fied. The real philanthropist can never rest upon a doctrine of temporary 
expediency. No system which seems to remove a present difficulty, by 
admitting a greater one at some distant period in the future, nor, indeed, IV 
INTRODUCTION 
permitting the eternity of its cause, will answer. With him flie weal and 
woe of the generations of men, thousands of centuries hence, is an object 
of solicitude, as well as the well-being of his co-existent fellow-beings and 
immediate descendants. Devoutly believing in some way in which all the 
seemingly intricate problems in human destiny are to be worked out in the 
good order of Divine Providence, he must have a theory which, 
“ From seeming evil still educes good; 
And vindicates the ways of God to man." 
Hence he can never adopt the notion of Malthus, which merely contem- 
plates killing off the surplus population; nor that of Doubleday, which 
would introduce the retrogressive principle of bodily depravity, in order 
to restrain the tendency to too rapid increase. Nor need he. The follow- 
ing pages unfold a theory of population based on the laws of organization, 
sustained by all the evidences of human and comparative anatomy and 
physiology, and demonstrated by the whole history of all the races of man- 
kind ; while the conclusion to which it arrives is precisely that best calcu- 
lated to enlist the sympathies and the prayers of every Christian—no 
slight presumptive evidence of its truthfulness. 
Nor is the knowledge of the doctrine here disclosed only important in 
enabling us to contemplate more hopefully the dim, uncertain future. It 
is replete with practical wisdom in the present tense. The same law, im- 
mutable and eternal as its Author, which insures the accomplishment of a 
brighter day—a millennial period—in the future history of our race, is in 
operation now. It always was in full force and virtue. And our duty, our 
present good, our improvement, development, and happiness, as well as our 
chance to be represented in the future generations, are intimately con- 
nected with a recognition of this law; for it is the law or progress. NEW THEOiiY OF POPULATION. 
“ In a very recent publication,” says Dr. Whately, “ I have 
seen mention made of a person who discovered the falsity of a 
certain doctrine (which, by the way, is nevertheless a true one, 
that of Malthus) instinctively. This kind of instinct, i. e., the 
habit of forming opinions at the suggestion rather of feeling than 
of reason, is very common.”* There can be little doubt that 
this remark refers to a passage in the preface to Doubleday’s 
“True Law of Population,” wherein the writer says: 
“ Happening many years ago, in the presence of a late relative, long 
since deceased, remarkable both for the sagacity and extended benevolence 
of his general views on philosophical subjects, to draw some of those 
startling, though not illogical, conclusions which seem to flow from theories 
then recently broached as to this subject, and much in vogue at the time, 
the reply was this: ‘ Depend upon it, my dear nephew, that you and I 
may safely decline to yield an implicit assent, though we may not, on the 
instant, be able to refute them, to views from which consequences, such 
as you have drawn, legitimately flow. Though I may not live to see it, 
nor you, a time will come when this mystery will be unvailed, and when a 
perhaps now mysterious, but beyond doubt, a beneficent law will be dis- 
covered, regulating this matter, in accordance with all the rest that we 
see of God’s moral government of the world.’ ” 
On comparing these extracts we cannot compliment Dr. 
Whately, either upon the fairness of his stricture or the depth 
of his insight. To apply the term instinctive to the conclusion 
thus drawn, indicates a misunderstanding of the mental process 
leading to it. Not a feeling, but a broad generalization is the 
basis on which such a conclusion rests. He who arrives at it in 
the manner above implied does so by comparing, in a more or 
* Introductory Lectures on Political Economy, 3d cdi\, p. IG3. 6 
A NEW THEORY OF POPULATION. 
less conscious way, the alleged truth with other truths, and dis- 
covering that it is not congruous with them. By daily accumu- 
lating experience he becomes impressed with the inherent tend- 
ency of things toward good—sees going on universally a patient 
self-rectification. He finds that the vis medicatrix natural—or 
rather the process which we describe by that expression—is not 
limited to the cure of wounds and diseases, but pervades creation. 
From the lowly fungus which, under varying circumstances, as- 
sumes varing forms of organization, up to the tree that grows 
obliquely, if it cannot otherwise get to the light—from the highest 
human faculty which increases or dwindles, according to the de- 
mands made on it, down to the polype, that changes its skin into 
stomach and its stomach into skin when turned inside out—he 
everywhere sees at work an essential beneficence. Equally in 
the attainment of fitness for a new climate, or skill in a new oc- 
cupation—in the diminution of a suppressed desire, and in the 
growing pleasure that attends the performance of a duty—in the 
gradual evanescence of grief, and in the callousness that follows 
long-continued privations — he perceives this remedial action. 
Whether he contemplates the acquirement, by each race, of a 
liking for the mode of life circumstances dictate—whether he re- 
gards the process by which different nations are slowly forced to 
produce those commodities only, that it is best for the world they 
should produce—or whether he looks at the repeated re-estab- 
lishment among a turbulent people, of the form of government 
best fitted for them—he is alike struck with the self-sufficingness 
of things. And when, after recognizing this throughout the whole 
organic world, he finds that it extends to the inorganic also—when 
he reads that though Newton feared for the stability of the solar 
system, yet Laplace found that all planetary perturbations are 
self-neutralizing—when he thus sees that perfection exists even 
where so high an intelligence failed to perceive it—he is still 
more convinced that in all cases we shall discover harmony and 
completeness when we know how to look for them. Hence, if 
any one propounds to him a theory implying in nature an in- 
eradicable defect, he hesitates to receive it. That the human 
constitution should include some condition which must ever con- 
tinue to entail either physical or moral pain, is at variance with A NEW THEORY OE POPULATION. 
7 
all that a wide experience teaches him. And finding the alleged 
fact conflict with universal facts, he concludes that it is probably 
untrue. He concludes this, not instinctively, but rationally, and 
his argument corresponds completely with the logical form—as 
in all other cases I have observed a certain sequence of phenome- 
na, I infer that there will be the same sequence in this case also. 
Moreover, such a belief is not only a rational, but the truly re- 
ligious one. Faith in the essential beneficence of things is the 
highest kind of faith. And considering his position, a little more 
of this faith would have been by no means unbecoming in the 
Archbishop of Dublin. 
But however right the point of view from which Mr. Double 
day, influenced by his relative, has studied the population ques 
tion, it does not follow that he has solved it. We are of opinion 
that he has not done so. There is one fact which seems to us at 
once fatal to his hypothesis; namely, that it does not fulfill the 
very condition which it purports to fulfill: it does not disclose a 
self-adjusting law. The theory which Mr. Doubleday seeks to 
establish is, that throughout both the animal and vegetable king- 
doms— 
“ Over-feeding checks increase ; while, on the other hand, a limited or 
deficient nutriment stimulates and adds to it.” (P. 17.) 
Or, as he elsewhere says— 
“ Be the range of the natural power to increase in any species what it 
may, the plethoric state invariably checks it, and the deplethoric state 
invariably develops it; and this happens in the exact ratio of the intensity 
and completeness of such state, until each state be carried so far as to 
bring about the actual death of the animal or plant itself.” (P. 20.) 
In this arrangement, Mr. Doubleday sees a guarantee for the 
maintenance of species. He argues that the plethoric state of 
the individuals constituting any race of organisms presupposes 
conditions so favorable to life that the race can be in no danger; 
and that rapidity of multiplication becomes needless. Conversely 
he argues that a deplethoric state implies unfavorable conditions 
—implies, consequently, unusual mortality; that is—implies a 
necessity for increased fertility to prevent the race from dying 
out. And hence, applying the law to mankind, he infers that 
there is a state of body intermediate between the plethoric and 8 
A NEW THEORY OF POPULATION. 
deplethoric, under which the rate of increase will not be greater 
than needful; and that a sufficient supply of good food to all, is 
the chief condition to the attainment of such a state. 
Now, without denying that there is some such law of variation 
as this which Mr. Doubleday points out, we hold that it cannot 
alone constitute the law of population, because, as already hinted, 
it does not really disclose a self-rectifying arrangement. We 
shall quickly see this on applying it to the human race as now 
existing. Mr. Doubleday will admit, or rather, will assert, that 
on the average mankind are at present in the deplethoric state; 
he will argue that the undue rate of increase commonly com- 
plained of results from this; and he will infer that to produce a 
comparatively plethoric state in all is the only remedy. But 
how, under the alleged law, can a comparatively plethoric state 
ever be attained to 1 If the present production of necessaries of 
life is insufficient for the normal nutrition of the race, and if the 
resulting deplethoric state involves that the next generation will 
greatly exceed the present in numbers, then, for any thing that 
appears to the contrary, the next generation will be in a more 
deplethoric state still. Unless Mr. Doubleday can show that the 
means of subsistence will increase more rapidly than the unduly 
fertile people, he cannot prove the existence of any remedial pro- 
cess. Nay, indeed, he must show that his law involves, under 
such circumstances, a greater increase of food than of people. 
Now' he neither does nor can show this; and thus the alleged law 
lacks that very property of self-adjustment, which he rightly re- 
gards as the test of the real law. 
Mr. Doubleday has given us, not the w'hole truth, but only a 
small fraction of it. He might, a, priori, have inferred this, bad 
he taken a wider view of the phenomena. For just the same ne- 
cessity that demands variations in the fertility of each race to 
balance variations in its mortality, still more imperatively de- 
mands variations in the fertilities of different races to balance 
variations in their mortalities; and whoever has duly familiarized 
himself with the simplicity and universality of natural agencies, 
can scarcely doubt that these minor variations of fertility observ- 
able in the same species, and these great variations of fertility which 
distinguish different species, are determined by the same cause. A NEW THEORY OF POPULATION. 
9 
Had Mr. Doubleday recognized this probability, he would have 
seen that no such special cause as that he assigns, was likely to be 
the true one; but that some more general cause must be looked 
for; and he would further have seen, that such more general 
cause was not to be discovered without inquiring more deeply 
into organic phenomena than he has done. 
Some clear idea of the nature of Life itself must, indeed, form 
a needful preliminary. We may be sure that a search for the in- 
fluences determining the maintenance and multiplication of living 
organisms, cannot be successfully carried out unless we under- 
stand what is the peculiar property of a living organism—what 
is the widest generalization of the phenomena that indicate life. 
By way of preparation, therefore, for the Theory of Population 
presently to be developed, we propose devoting a brief space to 
this prior question. 
And here we are at once met by the difficulty, that the widest, 
and it would appear also, the best definition of Life, is one that 
includes both the organic and inorganic. Startling though the 
assertion will be to most, it nevertheless seems true, that, as 
Coleridge, or rather Schelling, points out the characteristic which, 
manifested in a high degree, we call Life, is a characteristic man- 
ifested only in a lower degree by so-called inanimate objects. 
And hard as it is to believe this, yet the discoveries of chemists, 
who find that the alleged distinction between organic and inor- 
ganic compounds does not hold good, and the discoveries of 
physiologists, who are rapidly narrowing the once broad boundary 
line between the two divisions, day after day serve to confirm it. 
Hence, in seeking for a definition that shall distinguish organic 
existence from inorganic existence, we must not expect to find 
one that will be rigidly true in all cases. For if there be not 
such a line of demarkation in nature, no ingenuity of ours can 
establish one. All we can hope for is, some expression that shall 
conveniently classify the two, and shall be generally, though not 
universally, applicable. 
Employing the term, then, in its usual sense, as applicable only 
to organisms, Life may be defined as—the co-ordination of ac- 
tions. ' The growth of a crystal, which is the highest inorganic 
process we are acquainted with, involves but one action—that of A NEW THEORY OF POPULATION. 
10 
accretion. The growth of a cell, which is the lowest organic 
process, involves two actions—accretion and disintegration—re- 
pair and waste—assimilation and oxidation. Wholly deprive a 
cell of oxygen, and it becomes inert—ceases to manifest vital 
phenomena; or, as wre say, dies. Give it no matter to assimilate, 
and it wastes away and disappears, from continued oxidation. 
Evidently, then, it is in the balance of these twro actions that the 
life consists. It is not in the assimilation alone; for the crystal 
assimilates: neither is it in the oxidation alone; for oxidation is 
common to inorganic matter: but it is in the joint maintenance of 
these—the co-ordination of them. So long as the two go on 
together, life continues: suspend either of them, and the result is 
—death. 
The attribute which thus distinguishes the lowest organic from 
the highest inorganic bodies, similarly distinguishes the higher 
organisms from the lower ones. It is in the greater complexity 
of the co-ordination—that is, in the greater number and variety 
of the co-ordinated actions—that every advance in the scale of 
being essentially consists. And whether we regard the numer- 
ous vital processes carried on in a creature of complex structure 
as so many additional processes, or whether, more philosophically, 
we regard them as subdivisions of the two fundamental ones— 
oxidation and accretion—the co-ordination of them is still the life. 
Thus turning to what is physiologically classified as the vegetative 
system, we see that stomach, lungs, heart, liver, skin, and t'no 
rest, must work in concert. If one of them does too much or too 
little—that is, if the co-ordination be imperfect—the life is dis- 
turbed; and if one of them ceases to act—that is, if the co-ordi- 
nation be destroyed—the life is destroyed. So likewise is it with 
the animal system, which indirectly assists in co-ordinating the 
actions of the viscera by supplying food and oxygen. Its com- 
ponent parts, the limbs, senses, and instruments of attack or de- 
fense, must perform their several offices in proper sequence ; and 
further, must conjointly minister to the periodic demands of the 
viscera, that these may in turn supply blood. How completely 
the several attributes of animal life come within the definition, we 
shall best see on going through them seriatim. 
Thus Strength results from the co-ordination of actions; for it A NEW THEORY OF POPULATION. 
11 
is produced by the simultaneous contraction of many muscles and 
many fibers of each muscle; and the strength is great in propor- 
tion to the number of these acting together; that is, in propor- 
tion to the co-ordination. Swiftness, also, depending partly on 
strength, but requiring also the rapid alternation of movements, 
equally comes under the expression; seeing that, other things 
equal, the more quickly sequent actions can be made to follow 
each other, the more completely are they co-ordinated. So, too, 
is it with Agility; the power of a chamois to spring with safety 
from crag to crag implies accurate co-ordination in the move- 
ments of many different muscles, and a due subordination of them 
all to the perceptions. The definition similarly includes Instinct, 
which consists in the uniform succession of certain actions or series 
of actions after certain sensations or groups of sensations; and 
that which surprises us in instinct is the accuracy with which 
these compound actions respond to these compound sensations; 
that is, the completeness of their co-ordination. Thus, likewise, 
is it with Intelligence, even in its highest manifestations. That 
which we call rationality is the power to combine or co-ordi- 
nate a great number and a great variety of complex actions for 
the achievement of a desired result. The husbandman has in the 
course of years, by drainage and manuring, to bring his ground 
into a fertile state; in the autumn he must plow, harrow, and 
sow, for his next year’s crop ; must subsequently hoe and weed, 
keep out cattle, and scare away birds ; when harvest comes, must 
adapt the mode and time of getting in his produce to the weather 
and the labor market; he must afterward decide when, and where, 
and how to sell to the best advantage; and must do all this that 
he may get food and clothing for his family. By properly co-or- 
dinating these various processes (each of which involve many 
others), by choosing right modes, right times, right quantities, 
right qualities, and performing his acts in right order, he attains 
his end. But if he have done too little of this, or too much of 
that, or have done one thing when he should have done another 
—if his proceedings have been badly co-ordinated; that is, if he 
have lacked intelligence, he fails. 
We find, then, that the co-ordination of actions is a definition 
of Life, which includes alike its highest and its lowest manifes- 12 
A NEW THEORY OF POPULATION. 
tations, and not only so, but expresses likewise the degree of 
Life, seeing that the Life is high in proportion as the co-ordi 
nation is great. Proceeding upward, from the simplest organic 
cell in which there are but two interdependent actions, on through 
the group in which many such cells are acting in concert, on 
through the higher group in which some of these cells assume 
mainly the respiratory and others the assimilative function—pro- 
ceeding still to organisms in which these two functions are sub- 
divided into many others, and in which some cells begin to act 
together as contractile fibers; next to organisms in which the 
visceral division of labor is carried yet further, and in which 
many contractile fibers act together as muscles—ascending again 
to creatures that combine the movements of several limbs and 
many bones and muscles in one action ; and further, to creatures 
in which complex impressions are followed by the complex acts 
we term instinctive—and arriving finally at man, in whom not 
only are the separate acts complex, but who achieves his ends by 
combining together an immense number and variety of acts, 
often extending through years—we see that the progress is uni- 
formly toward greater co-ordination of actions. Moreover, this 
co-ordination of actions unconsciously constitutes the essence of 
our common notion of life; for we shall find, on inquiry, that 
when we infer the death of an animal, which does not move on 
being touched, we infer it because wre miss the usual co-ordina- 
tion of a sensation and a motion; and we shall also find, that the 
test by which we habitually rank creatures, high or low, in the 
scale of vitality, is the degree of co-ordination their actions exhibit. 
Further evidence that this is the true definition of life may be 
found in the fact, that the latest and most philosophical classifi- 
cation in zoology is based upon the structure of the co-ordinating 
apparatus, or what we commonly term the nervous system. 
Hunter aptly defined the function of the nerves as internuncial. 
That the separate parts of an organism may act in concert, a 
constant intercommunication must be kept up. This intercom- 
munication is maintained by the nerves; and there are no actions 
—visceral, muscular,perceptive, or other—but what are directed 
and adjusted by them. When, therefore, wc find that the modem 
division of the animal kingdom iuto Acrita, Nematoncura, Ho- A NEW THEORY OF POPULATION. 
13 
mogangliata, Ileterogangliata, and Vertebrata, is a division ex- 
pressive of the several forms of the internuncial or co-ordinating 
apparatus; and when, still more significantly, we find that these 
several classes rank according to the degree in which the co-ordi- 
nating apparatus is developed, and this, even up to man, in whom 
the development of it is the greatest; we have strong confirma- 
tion of the doctrine that Life and the co-ordination of actions 
are identical.* 
There remains but to notice the objection which possibly may 
be raised, that the co-ordination of actions is not life, but the abil- 
ity to maintain life. Lack of space forbids going into this at 
length. It must suffice to say, that life and the ability to main- 
tain life will be found the same. AVe perpetually expend the 
vitality we have that we may continue our vitality. Our power 
to breathe a minute hence depends upon our breathing now. We 
must digest during this week that we may have strength to digest 
next. That we may get more food, we must use the force which 
the food we have eaten gives us. Everywhere vigorous life is 
the strength, activity, and sagacity whereby life is maintained; 
and equally in descending the scale of being, or in watching the 
decline of an invalid, we see that the ebbing away of life is the 
ebbing away of the ability to preserve life. 
Ending here this preliminary dissertation, let us now proceed 
to our special subject. 
§ 1. On contemplating its general circumstances, we perceive 
that any race of organisms is subject to two sets of conflicting in- 
fluences. On the one hand by natural death, by enemies, by lack 
of food, by atmospheric changes, etc., it is constantly being des- 
troyed. On the other hand, partly by the strength, swiftness, 
and sagacity of its members, and partly by their fertility, it is 
constantly being maintained. These conflicting sets of influences 
may be conveniently generalized as—the forces destructive of 
race, and the forces preservative of race. 
§ 2. While any race continues to exist, the forces destructive 
* It may be needful to remark, that by the proposed expression it is intended to define 
—not Life in its esseuce; but, Life as manifested to us—not Life as a noumenon; bur 
Life as a phenomenon. The ultimate mystery is as great as ever; seeing that there r« 
mains unsolved the question—What determines the co-ordinations of actions J 14 
A NEW THEORY OF POPULATION. 
of it and the forces preservative of it must perpetually tend 
toward equilibrium. If the forces destructive of it decrease, the 
race must gradually become more numerous, until, either from 
lack of food or from increase of enemies, the destroying forces 
again balance the preserving forces. If, reversely, the forces 
destructive of it increase, then the race must diminish until, 
either from its food becoming relatively more abundant, or from 
its enemies dying of hunger, the destroying forces sink to the 
level of the preserving forces. Should the destroying forces be 
of a kind that cannot be thus met (as great change of climate), 
the race, by becoming extinct, is removed out of the category. 
Hence this is necessarily the law of maintenance of all races ; see- 
ing that when they cease to conform to it they cease to be. 
Now the forces preservative of race are two—ability in each 
member of the race to preserve itself, and ability to produce 
other members—power to maintain individual life, and power to 
propagate the species. These must vary inversely. When, from 
lowness of organization, the ability to contend with external 
dangers is small, there must be great fertility to compensate for 
the consequent mortality; otherwise the race must die out. 
When, on the contrary, high endowments give much capacity of 
self-preservation, there needs a correspondingly low degree of 
fertility. Given the dangers to be met as a constant quantity ; 
then, as to the ability of any species to meet them must be a 
constant quantity too, and as this is made up of the two factors 
—power to maintain individual life and power to multiply—these 
cannot do other than vary inversely. 
§ 3. To show that observed phenomena harmonize with this d 
jpriori principle seems scarcely needful. But, though axiomatic 
in its character, and therefore incapable of being rendered more 
certain, yet illustrations of the conformity to it which nature 
everywhere exhibits, will facilitate the general apprehension of it. 
In the vegetable kingdom we find that the species consisting 
of simple cells, exhibit the highest reproductive power. The 
yeast fungus, which in a few propagates itself throughout a 
large mass of wort, offers a familiar example of the extreme ra- 
pidity with which these lowly organisms multiply. In the Pro- 
tococcus nivalis, a microscopic plant which in the course of a night A NEW THEORY OF POPULATION. 
15 
reddens many square miles of snow, we have a like example; as 
also in the minute Algce, which color the vraters of stagnant 
pools. The sudden appearance of green films on damp, decaying 
surfaces, the spread of mold over stale food, and the rapid de- 
struction of crops by mildew, afford further instance. If we as 
cend a step to plants of appreciable size, we still find that in 
proportion as the organization is low the fertility is great. Thus 
of the common puff-ball, which is little more than a mere aggre- 
gation of cells, Fries says, “in a single individual of Reticuluria 
maxima, I have counted (calculated X) 10,000,000 sporules.” 
From this point upward, increase of bulk and greater complexity 
of structure are still accompanied by diminished reproductive 
power: instance the Macrocystis pyrifera, a gigantic sea-weed, 
which sometimes attains a length of 1,500 feet, of which Carpen- 
ter remarks, “ This development of the nutritive surface takes 
place at the expense of the fructifying apparatus, which is here 
quite subordinate.”* And when wre arrive at the highly organ- 
ized exogenous trees, we find that not only are they many years 
before beginning to bear with any abundance, but that even then 
they produce, at the outside, but a few thousand seeds in a 
twelvemonth. During its centuries of existence, pn oak does 
not develop as many acorns as a fungus docs spores in a single 
night. 
Still more clearly is this truth illustrated throughout the ani- 
mal kingdom. Though not so great as the fertility of the Pro- 
tophyta, which, as Professor Ilenslow says, in some cases passes 
comprehension, the fertility of the Protozoa is yet almost beyond 
belief. In the polygastric animalcules spontaneous fission takes 
place so rapidly that “it has been calculated by Professor Ehren- 
berg that no fewrer than 268,000,000 might be produced in a 
month from a single Paramecium \ and even this astonishing 
rate of increase is far exceeded in another species, one individual 
of which, “ only to be perceived by means of a high magnifying 
power, is calculated to generate 170,000,000 in four days.”J 
Among the larger organisms exhibiting this lowest mode of re- 
production under a modified form—that of gemmation—wre see 
i 
* Prin. of I’hys., 3d edit , p. 77. 
t Ibid., 3d edit., p. 249. 
} Ibid., p. 124. 16 
A NEW THEORY OF POPULATION. 
that, though not nearly so rapid as in the Infusoria, the rate of 
multiplication is still extremely high. This fact is well illustrated 
by the polypes ; and in the apparent suddenness with which 
whole districts are blighted by the Aphis (multiplying by inter 
nal gemmation), we have a familiar instance of the startling ro 
suits which the parthenogenetic process can achieve. Where 
reproduction becomes occasional instead of continuous, as it does 
among higher creatures, the fertility equally bears an inverse 
ratio to the development. “The queen ant of the African Ter- 
mites lays 80,000 eggs in twenty-four hours; and the common 
hair worm (Gordius) as many as 8,000,000 in less than one 
day.”* Among the Vertebrata, the lowest are still the most 
prolific. “ It has been calculated,” says Carpenter, “ that above 
a million of eggs are produced at once by a single codfish.”f In 
the strong and sagacious shark comparatively few are found. Still 
less fertile are the higher reptiles. And among the Mammalia, 
beginning with small Rodents, which quickly reach maturity, 
produce large litters, and several litters in the year; advancing 
step by step to the higher mammals, some of which are long in 
attaining the reproductive age, others of which produce but one 
litter in a year, others but one young one at a time, others who 
unite these peculiarities; and ending with the elephant and man, 
the least prolific of all, we find that throughout this class, as 
throughout the rest, ability to multiply decreases as ability to 
maintain individual life increases. 
§ 4. The a priori principle thus exemplified has an obverse of 
a like axiomatic character. We have seen that for the continu- 
ance of any race of organisms it is needful that the power of 
selfpreservation and the power of reproduction should vary in- 
versely. We shall now see that, quite irrespective of such an end 
to be subserved, these powers could not do otherwise than vary 
inversely. In the nature of things, species can subsist only by 
conforming to this law; and equally in the nature of things they 
cannot help conforming to it. 
Reproduction, under all its forms, may be described as th* 
separation of portions of a parent plant or animal for the purpose 
* Agassiz and Gould, p. 274. 
t Prin. of Phyi., 3d edit, p. 964 THEORY OF POPULATION. 
17 
of forming other plants or animals. Whether it be by spontane- 
ous fission, by gemmation, or by gemmules; whether the de- 
tached products be bulbels, spores, or seeds, ovisacs, ova or sperm- 
atozoa ; or however the process of multiplication be modified, it 
essentially consists in the throwing off of parts of adult organ- 
isms for the purpose of making new organisms. On the other 
hand, self-preservation is fundamentally a maintenance of the 
organism in undiminished bulk. Among the lowest forms of 
life, aggregation of tissue is the only mode in which the self- 
preserving power is shown. Even in the highest, sustaining the 
body in its integrity is that in which self-preservation most truly 
consists—is the end which the widest intelligence is indirectly 
made to subserve. While, on the one side, it cannot be denied 
that the increase of tissue constituting growth is self-preservation 
both in essence and in result; neither can it, on the other side, be 
denied that a diminution of tissue, either from injury, disease, or 
old age, is in both essence and result the reverse. 
Hence the maintenance of the individual and the propagation 
of the race, being respectively aggregative and separative, neces- 
sarily vary inversely. Every generative product is a deduction 
from the parental life; and, as already pointed out, to diminish 
life is to diminish the ability to preserve life. The portion 
thrown off is organized matter; vital force has been expended in 
the organization of it, and in the assimilation of its component 
elements; which vital force, had no such portion been made and 
thrown off, would have been available for the preservation of the 
parent. 
Neither of these forces, therefore, can increase, save at the ex- 
pense of the other. The oue draws in and incorporates new ma- 
terial ; the other throws oft’ material previously incorporated. 
The one adds to; the other takes from. Using a convenient 
expression for describing the facts (though one that must not be 
construed into an hypothesis), we may say that the force which 
builds up and repairs the individual is an attractive force, while 
that which throws off germs is a repulsive force. But whatever 
may turn out to be the true nature of the two processes, it is clear 
that they are mutually destructive; or, stating the proposition in 
its briefest form—Individuation and .Reproduction are antagonistic. 18 
A NEW THEORY OF POPULATION. 
Again, illustrating the abstract by reference to the concrete, 
let us now trace throughout the organic world the various phases 
of this antagonism. 
§ 5. All the lowest animal and vegetable firms—Protozoa and 
Protophyta—consist essentially of a single cell containing fluid, 
and having usually a solid nucleus. This is true of the Infusoria, 
the simplest Entozoa, and the microscopic Algae und Fungi. The 
organisms so constituted uniformly'multiply by spontaneous fis- 
sion. The nucleus, originally spherical, becomes elongated, then 
constricted across its smallest diameter, and ultimately separates, 
when “its divisions,” says Professor Owen, describing the pro- 
cess in the Infusoria, “seem to repel each other to positions equi- 
distant from each other, and from the pole or end of the body to 
which they are nearest. The influence of these distinct centers 
of assimilation is to divert the flow of the plasmatic fluid from a 
common course through the body of the polygastrian to two 
special courses about those centers. So much of the primary 
developmental process is renewed, as leads to the insulation of 
the sphere of the influence of each assimilative center from that 
of the other by the progressive formation of a double party-wall 
of integument, attended by progressive separation of one party- 
wall from the other, and by concomitant constriction of the body 
of the polygastrian, until the vibratile action of the superficial 
cilia of each separating moiety severs the narrow neck of union, 
and they become two distinct individuals.”* Similar in its gen- 
eral view is Dr. Carpenter’s description of the multiplication of 
vegetable cells, which he says divide, “ in virtue, it may be sur- 
mised, of a sort of mutual repulsion between the two halves of 
the endochrome (colored cell-contents) which leads to their spon- 
taneous separation.”! Under a modified form of this process 
the cell-contents, instead of undergoing bisection, divide into 
numerous parts, each of which ultimately becomes a separate in- 
dividual. In some of the Algae “ a whole brood of young cells 
may thus be at once generated in the cavity of the parent-cell, 
which subsequently bursts and sets them frec.”J The Achlya 
proli/era multiplies after this fashion. Among the Fungi, too, 
* Parthenogenesis p. 8. 
t Prin. of Phy«.t p. 92. 
t Ibid., p. 93. A NEW THEORY OF POPULATION. 
19 
the same mode of increase is exemplified by the Protococcus ni- 
valis. And, “ it would appear that certain Infusoria, especially 
the Kolpodincc, propagate by the breaking-up of their own mass 
into reproductive particles.”* 
Now in this fissiparous mode of multiplication, which “is 
amazingly productive, and indeed surpasses in fertility any other 
with which we are acquainted,”f we see most clearly the antago- 
nism between individuation and reproduction. We see that tho 
reproductive process involves destruction of the individual; for 
in becoming two the parent fungus or polygastrian must be held 
to lose its own proper existence; and when it breaks up into a 
numerous progeny, does so still more completely. Moreover, 
this rapid mode of multiplication not only destroys the indi- 
viduals in whom it takes place, but also involves that their indi- 
vidualities, while they continue, shall be of the lowest kind. For 
assume a protozoon to be growing by imbibition at a given rate, 
and it follows that the oftener it divides the smaller must be the 
size it attains to; that is, the smaller the development of its 
individuality. And a further manifestation of the same truth is 
seen in the fact, that the more frequent the spontaneous fission 
the shorter the existence of each individual. So that alike by 
p/eventing any thing beyond a microscopic bulk being attained, 
by preventing the continuance of this in its integrity beyond a 
few hours, and by being fatal when it occurs, this most active 
mode of reproduction shows the extremest antagonism to indi- 
vidual life. 
§ 6. Whether or not we regard reproduction as resulting from 
a repulsive force (and, as seen above, both Owen and Carpenter 
lean to some such view), and whether or not we consider the 
formation of the individual as due to the reverse of this—an 
attractive force—we cannot, on studying the phenomena, help 
admitting that two opposite activities thus generalized are at 
work; we cannot help admitting that the aggregative and sepa- 
rative tendencies do in each case determine the respective devel- 
opments of the individual and the race. On ascending one 
* Prin. of Phys., p. 917. 
t A General Outline of the Animal Kingdom. Ey Prof. T. R. Jones, F.G.S., p. 61. 20 
A NEW THEORY OF POPULATION. 
degree in the scale of organic life, we shall find this truth clearly 
exemplified. 
For if these single-celled organisms which multiply so rapidly 
be supposed to lose some of their separative tendency, what must 
be the result ? They now not only divide frequently, but the 
divided portions fly apart. How, then, will a diminution of this 
separative tendency first show itself? May we not expect that 
it will show itself in the divided portions not flying apart, but 
remaining near each other, and forming a group ? This we find 
in nature f.o be the first step in advance. The lowest compound 
organisms are “ simple aggregations of vesicles without any defi- 
nite arrangement, sometimes united, but capable of existing sepai'- 
ately.v* In these cases, “ every component cell of the aggregate 
mass that springs from a single germ, being capable of existing 
independently of the rest, may be regarded as a distinct indi- 
vidual.”! The several stages of this aggregation are very clearly 
seen in both the animal and vegetable kingdoms. In the litem- 
atococcus binalis, the plant producing the reddish slime seen on 
damp surfaces, not only does each of the cells retain its original 
sphericity, but each is separated from its neighbor by a wide 
interval filled with mucus; so that it is only as being diffused 
through a mass of mucus common to them all, that these cells 
can be held to constitute one individual. We find, too, that 
“the component cells, even in the highest Algae, are generally 
separated from each other by a large quantity of mucilaginous 
intercellular substance.”! And, again, the tissue, of the simpler 
Lichens, “ in consequence of the very slight adhesion of its com- 
ponent cells, is said to be pulverulent.Ӥ Similarly the Protozoa, 
by their feeble union, constitute the organisms next above them. 
Among the Polygastrica there are many cases “ in which the 
individuals produced by fission or gemmation do not become 
completely detached from each other.” || The Ophrydium, for 
instance, “ exists under the form of a motionless jelly-like mass 
. . . made up of millions of distinct and similar individuals 
imbedded in a gelatinous connecting and again, the 
* Carpenter. t Vrin. of I'bys., p. 873 f Ibid., p. 203. § Ibid., p. 209. 
|| Ibid., 1 249. If Ibid., p. 249. A NEW THEORY OP POPULATION 
21 
Uvella, or “grape monad,” consists of a cluster “ which strongly 
resembles a transparent mulberry rolling itself across the field of 
view by the ciliary action of its component individuals.”* The 
parenchyma of the Sponge, too, is made up of cells “ each of 
which has the character of a distinct animalcule, having a certain 
power of spontaneous motion, obtaining and assimilating its own 
food, and altogether living by and for itself;” and so small is the 
cohesion of these individual cells, that the tissue they constitute 
“drains away when the mass is removed from the water, like 
white of egg.”f 
Of course in proportion as the aggregative tendency leading to 
the formation of these groups of monads is strong, we may ex- 
pect that, other things equal, the groups will be large. Proceed- 
ing upward from the yeast fungus, whose cells hold together in 
groups of four, five, and six.J there must be found in each species 
of these composite organisms a size of group determined by the 
strength of the aggregative tendency in that species. Hence we 
may expect that, when this limit is passed, the group no longer 
remains united, but divides. Such we find to be the fact. These 
groups of cells undergo the same process that the cells themselves 
do. They increase up to a certain point, and then multiply either 
by simple spontaneous fission or by that modification of it called 
gemmation. The Volvox globator, which is made up of a number 
of monads associated together in the form of a hollow sphere, de- 
velops within itself a number of smaller spheres similarly consti- 
tuted ; and after these, swimming freely in its interior, have 
reached a certain size, the parent group of animalcules bursts, and 
sets the interior groups free. And here we may observe how 
this compound individuality of the Volvox is destroyed in the 
act of reproduction, as the simple individuality of the monad is. 
Again, in the higher forms of grouped cells, where something like 
organization begins to show itself, the aggregations are not only 
larger, but the separative pnocess, now carried on by the method 
of gemmation, no longer wholly destroys the individual. And 
in fact, this gemmation may be regarded as the form which spon- 
taneous fission must assume in ceasing to be fatal; seeing that 
* Prin. of Phys., p. 250. t Ibid., p. 25(5. t Ibid., p. 212. 22 
A NEW THEORY OP POPULATION. 
gemmation essentially consists in the separation, not into halves, 
but into a larger part and a smaller part; the larger part con- 
tinuing to represent the original individual. Thus in the common 
Hydra, or fresh-water polype, “ little bud-like processes are de- 
veloped from the external surface, which are soon observed to 
resemble the parent in character, possessing a digestive sac, 
mouth, and tentacula; for a long time, however, their cavity is 
connected with that of the parent; but at last the communication 
is cut off, and the young polype quits its attachment, and goes in 
quest of its own maintenance.”* 
§ 7. Progress from these forms of organization to still higher 
forms is similarly characterized by increase of the aggregative 
tendency or diminution of the separative, and similarly exhibits 
the necessary antagonism between the development of the indi- 
vidual and the increase of the race. That process of grouping 
which constitutes the first step toward the production of complex 
organisms, we shall now find repeated in the formation of series 
of groups. Just as a diminution of the separative tendency is 
shown in the aggregation of divided monads, so is a further dimi- 
nution of it show'll in the aggregation of the divided groups of 
monads. The first instance that occurs is afforded by the com- 
pound polypes. “ Some of the simpler forms of the composite 
Hydroida,” says Carpenter, “ may be likened to a Hydra, whose 
gemmse, instead of becoming detached, remain permanently con- 
nected with the parent; and as these in their turn may develop 
gemmae from their own bodies, a structure of more or less arbor- 
escent character may be produced.”f A similar species of combi- 
nation is observable among the Bryozoa, and the compound 
Tunicata. Every degree of union may be found among these 
associated organisms; from the one extreme in which the indi- 
viduals can exist as well apart as together, to the other extreme 
in which the individuals are lost in the general mass. While 
each Bryozoon is tolerably independent of its neighbor, “ in the 
compound Hydroida, the lives of the polypes are subordinate to 
that of the polypdom.”J Of the Salpidce and Pyrosornida;, Car- 
penter says:—“ Although closely attached to one another, these 
* Prin. of l’hya., p. 266. t Ibid., 267. t Ibid., p. 276. A NEW THEORY OF POPULATION. 
23 
associated animals are capable of being separated by a smart 
shock applied to the sides of the vessel in which they are swim- 
ming. . . . In other species, however, the separate animals 
arc imbedded in a gelatinous mass,” and in one kind “ there is an 
absolute union between the vascular systems of the different in- 
dividuals.”* 
In the same manner that with a given aggregative tendency 
there is a limit to the size of groups, so is there a similarly-de- 
termined limit to the size of series of groups; and that spontane- 
ous fission which we have seen in cells and groups of cells we 
here find repeated. In the lower Annelida, for example, “ after 
the number of segments in the body has been greatly multiplied 
by gemmation, a separation of those of the posterior portion be- 
gins to take place ; a constriction forms itself about the beginning 
of the posterior third of the body, in front of which the alimen- 
tary canal undergoes a dilatation, while on the segment behind 
it a proboscis and eyes are developed, so as to form the head of 
the young animal which is to be budded off; and in due time, 
by the narrowing of the constriction a complete separation is 
effected.”f Not un frequently in the No is this process is re- 
peated in the young one before it becomes independent of the 
parent. The higher Annelida are distinguished by the greater 
number of segments held in continuity; an obvious result of 
comparatively infrequent fission. In the class Myriapoda, which 
stands next above, “ there is no known instance of multiplication 
by fission.Yet even here the law may be traced both in the 
number and structure of the segments. The length of the body 
is still increased after birth “ by gemmation from (or partial 
fission of) the penultimate segment.” The lower members of 
the class are distinguished from the higher by the greater extent 
to which this gemmation is carried. Moreover, the growing 
aggregative tendency is seen in the fact, that each segment 
of the Julus “is formed by the coalescence of two original 
segments,Ӥ while in the Scolopendridce, which are the high- 
est of this class, “the head, according to Mr. Newport, is com 
* Prin of Phys , 2d edit., p. 1!5. t Ibid., p. 954. J Ibid., p. 958. 
§ Ibid., p. 686 24 
A NEW THEORY OF POPULATION. 
posed of eight segments, which are often consolidated into one 
piece both of which phenomena may be understood as ar- 
rests of the process of fission, which, if allowed to go a little 
further, would have produced distinct segments; and, if allowed 
to go further still, wrould have separated these segments into 
groups. 
§ 8. Remarking, first, how gradually this mode of multiplica- 
tion disappears—how there are some creatures that spontaneously 
divide or not, according to circumstances; other that divide when 
in danger (the several parts being capable of growing into com- 
plete individuals) ; others which, though not self-dividing, can live 
on in each half if artificially divided; and others in which only 
one of the divided halves can live—how, again, in the Crusta- 
ceans the power is limited to the reproduction of lost limbs; how 
there arc certain reptiles that can re-supply a lost tail, but only 
imperfectly ; and how among the higher Vcrtebratu the ability to 
repair small injuries is all that remains—remarking thus much, 
let us now, by way of preparation for what is to follow, consider 
the significance of the foregoing facts, taken in connection with 
the definition of Life awhile since given. 
This spontaneous fission, which wre have seen to be, in all 
cases, more or less destructive of individual life, is simply a ces- 
sation in the co-ordination of actions. From the single cell, the 
halves of whose nucleus, instead of continuing to act together, 
begin to repel each other, fiy apart, establish dictinct centers of 
assimilation, and finally cause the cell to divide; up to the An- 
nelidan, whose string of segments separates, after reaching a 
certain length; wre everywhere see the phenomenon to be funda- 
mentally this. The tendency to separate is the tendency not to 
act together, probably arising from inability to act together any 
longer; and the process of separation is the process of ceasing to 
act together. How truly non-co-ordination is the essence of the 
matter, will be seen on observing that fission takes place more or 
less rapidly, according as the co-ordinating apparatus is less or 
more developed. Thus, “ the capability of spontaneous division 
is one of the most distinctive attributes of the acrite type of 
* Pi-in. of Phy»., 2d edit., p. 958. A NEW THEORY OF POPULATION. 
25 
structure the acrite type of structure being that in which the 
neurine or nervous matter is supposed to be diffused through the 
tissues in a molecular state, and in which, therefore, there exists 
no distinct nervous or co-ordinating system. From this point 
upward the gradual disappearance of spontaneous fission is 
clearly related to the gradual appearance of nerves and ganglia— 
a fact well exemplified by the several grades of Annelida and 
Myriapoda. And when we remember that in the embryotic de- 
velopment of these classes, the nervous system does not make its 
appearance until after the rest of the organism has made great 
progress, we may even suspect that that coalescence of segments 
characteristic of the Myriapoda, exhibits the co-ordinating power 
of the rapidly-growing nervous system overtaking and arresting 
the separative tendency; and doing this most where it (the nerv- 
ous system) is most developed, namely, in the head. 
And here let us remark, in passing, how, from this point of 
view, we still more clearly discern the antagonism of individu- 
ation and reproduction. We before saw that the propagation of 
the race is at the expense of the individual: in the above facts we 
may contemplate the obverse of this—may see that the formation 
of the individual is at the expense of the race. This combination 
of parts that are tending to separate and become distinct beings 
—this union of many incipient minor individualities into one 
large individuality—is an arrest of reproduction—a diminution 
in the number produced. Either these units may part and lead 
independent lives, or they may remain together and have their 
actions co-ordinated. Either they may, by their diffusion, form 
a small, simple, and prolific race, or, by their aggregation, a large, 
complex, and infertile one. But manifestly the aggregation in- 
volves the infertility; and the fertility involves the smallness. 
§ 9. The ability to multiply by spontaneous fission, and the 
ability to maintain individual life, are opposed in yet another 
mode. It is not in respect of size only, but still more in respect 
of structure, that the antagonism exists. 
Higher organisms are distinguished from lower ones partly by 
bulk, and partly by complexity. This complexity essentially 
* A General Outline of the Animal Kingdom. By Professor T. R. Jones, p. 61,. 26 
A NEW THEORY OF POPULATION 
consists in the mutual dependence of numerous different organs, 
each subserving the lives of the rest, and each living by the help 
of the rest. Instead of being made up of many like parts, per- 
forming like functions, as the Crinoid, the Star-fish, or the Milli- 
pede, a vertebrate animal is made up of many unlike parts, per- 
forming unlike functions. From that initial form of a compound 
organism, in which a number of minor individuals are simply 
grouped together, we may, more or less distinctly, trace not only 
the increasing closeness of their union, and the gradual disappear- 
ance of their individualities in that of the mass, but the gradual 
assumption by them of special duties. And this “ physiological 
division of labor,” as it has been termed, has the same effect as 
the division of labor among men. As the preservation of a 
number of persons is better secured when, uniting in a society, 
they severally undertake different kinds of work, than when they 
are separate, and each performs for himself every kind of work ; 
so the preservation of a congeries of parts, which, combining into 
one organism, respectively assume nutrition, respiration, circula- 
tion, locomotion, as separate functions, is better secured than 
when those parts are independent, and each fulfills for itself all 
these functions. 
But the condition under which this increased ability to main- 
tain life becomes possible is, that the parts shall cease to sepa- 
rate. If they are perpetually separating, it is clear that they 
cannot assume mutually subservient duties. And it is further 
clear that the more the tendency to separate diminishes, that is, 
the larger the groups that remain connected, the more minutely 
and perfectly can that subdivision of functions which we call organ- 
ization be carried out. 
Thus we see that in its most active form the ability to multi- 
ply is antagonistic to the ability to maintain individual life, not 
only as preventing increase of bulk, but also as preventing or- 
ganization—not only as preventing homogeneous co-ordination, 
but as preventing heterogeneous co-ordination. 
§ 10. To establish the unbroken continuity of this law of fer- 
tility, it will be needful, before tracing its results among the 
higher animals, to explain in what manner spontaneous fission is 
now understood, and what the cessation of it essentially means. A NEW THEORY OF POPULATION. 
27 
Originally naturalists supposed that creatures which multiply by 
self-division, under any of its several forms, continue so to mul- 
tiply perpetually. In many cases, however, it has latterly been 
shown that they do not do this; and it is now becoming a re- 
ceived opinion that they do not, and cannot, do this, in any case. 
A fertilized germ appears here, as among higher organisms, to be 
the point of departure; and that constant formation of new tissue 
implied in the production of a great number of individuals by 
fission, seems gradually to exhaust the germinal capacity in the 
same way that the constant formation of new tissue, during the 
development of a single mammal, exhausts it. The phenomena 
classified by Steenstrup as “ Alternate Generation,” and since 
generalized by Professor Owen in his work “ On Parthenogen- 
esis,” illustrate this. The egg of a Medusa (jelly-fish) develops 
into a polypoid animal, called the Strobila. This Strobila lives 
as the polype does, and, like it, multiplies rapidly by gemmation. 
After a great number of individuals have been thus produced, 
and when, as we must suppose, the germinal capacity is ap- 
proaching exhaustion, each Strobila begins to exhibit a scries of 
constrictions, giving it some resemblance to a rouleau of coin or 
a pile of saucers. These constrictions deepen ; the segments 
gradually develop tentacula; the terminal segment finally separ- 
ates itself, and swims away in the form of a young Medusa; the 
other segments, in succession, do the same; and from the eggs 
which these Medusae produce, other like series of polypoid ani- 
mals, multiplying by gemmation, originate. In the compound 
Polypes, in the Tunicata, in the Trematoda, and in the Aphis, 
we have repeated, under various modifications, the same phe- 
nomenon. 
Understanding, then, this lowest and most rapid mode of mul- 
tiplication to consist essentially in the production of a great 
number of individuals from a single germ—perceiving, further, 
that diminished activity of this mode of multiplication consists 
essentially in the aggregation of the germ-product into larger 
masses—and seeing, lastly, that the disappearance of this mode 
of multiplication consists essentially in the aggregation of the 
germ-product into one mass—we shall be in a position to com 
prehend, among the higher animals, that new aspect of the lav>, 28 
A NEW THEORY OF POPULATION. 
under which increased individuation still involves diminished 
reproduction. Progressing from those lowest forms of life in 
which a single ovum originates countless organisms, through the 
successive stages in which the number of organisms so originated 
becomes smaller and smaller; and finally arriving at a stage in 
which one ovum produces but one organism; we have now, in 
our further ascent, to observe the modified mode in which this 
same necessary antagonism between the ability to multiply, and 
the ability to preserve individual life, is exhibited. 
§ 11. Throughout both the animal and vegetable kingdoms, 
generation is effected “ by the union of the contents of a ‘ sperm- 
cell ’ with those of a ‘ germ-cellthe latter being that from within 
which the embryo is evolved, while the former supplies some 
material or influence necessary to its evolution.”* Among the 
lowest vegetable organisms, as in the Desmidece, the l)iutoin«ceoe, 
and other families of the inferior Algce, these cells do not appre- 
ciably differ; and the application to them of the terms “ sperm- 
cell ” and “ germ-cell” is hypothetical. From this point upward, 
however, distinctions become visible. As we advance to higher 
and higher types of structure, marked differences arise in the 
character of these cells, in the organs evolving them, and in the 
position of these organs, which arc finally located in separate 
sexes. Doubtless a separation in the functions of “ sperm-cell” 
and “ germ-cell ” has simultaneously arisen. That change from 
homogeneity of function to heterogeneity of function which essen- 
tially constitutes progress in organization may be assumed to 
take place here also; and, indeed, it is probable that the distinc- 
tion gradually established between these cells, in origin and ap- 
pearance, is merely significant of and consequent upon, the dis- 
tinction that has arisen between them in constitution and office. 
Let us now inquire in what this distinction consists. 
If the foundation of every new organism be laid by the combi- 
nation of two elements, we may reasonably suspect that these 
two elements are typical of some two fundamental divisions of 
which the new organism is to consist. As nothing in nature is 
without meaning and purpose, we may be sure that the univer- 
* Prin. of Phya., p. 907. A NEW THEORY OF POPULATION. 
29 
sality of this binary origin, signifies the universality of a binary 
structure. The simplest and broadest division of which an organ- 
ism is capable must be that signified. What, then, must this 
division be 1 
The proposed definition of organic life supplies an answer. If 
organic life be the co-ordination of actions, then an organism may 
be primarily divided into parts whose actions are co-ordinated, 
and parts which co-ordinate them—organs which are made to 
work in concert, and the apparatus which makes them so work— 
or, in other words, the assimilative, vascular, excretory, and 
muscular systems on the one hand, and the nervous system on 
the other. The justness of this classification will become further 
apparent, when it is remembered that by the nervous system 
alone is the individuality established By it all parts are made 
one in purpose, instead of separate; by it the organism is ren- 
dered a conscious whole—is enabled to recognize its own extent 
and limits; and by it are all injuries notified, repairs directed, 
and the general conservation secured. The more the nervous 
system is developed, the more reciprocally subservient do the 
components of the body become—the less can they bear separ- 
ating. And that which thus individuates many parts into one 
whole, must be considered as more broadly distinguished from 
the parts individuated, than any of these parts from each other. 
Further evidence in support of this position may be drawn from 
the fact, that as we ascend in the scale of animal life, that is, 
as the co-ordination of actions becomes greater, we find the 
co-ordinating or nervous system becoming more and more def- 
initely separated from the rest; and in the vertebrate or high- 
est type of structure we find the division above insisted on 
distinctily marked. The co-ordinating parts and the parts co- 
ordinated are placed on opposite sides of the vertebral column. 
With the exception of a few ganglia, the whole of the nervous 
masses are contained within the neural arches of the vertebrae; 
while all the viscera and limbs are contained within, or appended 
to, the haemal arches—the terms neural and haemal having, in- 
deed, been chosen to express this fundamental division. 
If, then, there be truth in the assumption that the two elements, 
which, by their union, give origin to a new' organism, typify the 30 
A NEW THEORY OF POPULATION. 
two essential constituents of such new organism, we must infer 
that the sperm-cell and genn-cell respectively consist of co-or- 
dinating matter and matter to be co-ordinated — neurine and 
nutriment. That apparent identity of sperm-cell and genn-cell 
seen in the lowest forms of life may thus be understood as sig- 
nificant of the fact that no extended co-ordination of actions 
exists in the generative product—each cell being a separate indi- 
vidual ; and the dissimilarity seen in higher organic types as 
expressive of, and consequent upon, the increasing degree of co- 
ordination exhibited.”* 
That the sperm-cell and germ-cell are thus contrasted in nature 
and function may further be suspected on considering the dis- 
tinctive characteristics of the sexes. Of the two elements they 
respectively contribute to the formation of a fertile germ, it may 
be reasonably supposed that each furnishes that which it pos- 
sesses in greatest abundance and can best spare. Well, in the 
greater size of the nervous centers in the male, as well as in the 
fact that during famines men succumb sooner than women, we 
see that in the male the co-ordinating system is relatively pre- 
dominant. From the same evidence, as well as from the greater 
abundance of the cellular and adipose tissues in women, we may 
infer that the nutritive system predominates in the female.f 
Here, then, is additional support for the hypothesis that the 
sperm-cell, which is supplied by the male, contains co-ordinating 
matter, and the germ-cell, which is supplied by the female, con- 
tains matter to be co-ordinated. 
The same inference may, again, be drawn from a general view 
of the maternal function. For if, as we see, it is the office of the 
mother to afford milk to the infant, and during a previous period 
to afford blood to the foetus, it becomes probable that during a 
yet earlier stage it is still the function to supply nutriment, though 
* Should it be objected that in the higher plants the sperm-cell and germ-cell differ, 
though no distinct co-ordinating system exists, it is replied that there it co-ordination 
of actions, though of a feeble kind, and that there mu9t be some agency by which this 
is carried on. 
t It is a significant fact that among the dioecious invertebrata, where the nutritive sys- 
tem greatly exceeds the other systems in development, the female is commonly the 
largest, and often greatly so. In some of the Rotifera the male has no nutritive system 
at all. See Prin. of Phyt., p. 954. A NEW THEORY OP POPULATION. 
31 
in another form. Indeed, when, ascending gradually the scale of 
animal life, we perceive that this supplying of milk, and before 
that of blood, is simply a continuation of the previous process, 
we may be sure that, with Nature’s usual consistency, this pro- 
cess is essentially one from the beginning. 
Quite in harmony with this hypothesis concerning the respect- 
ive natures of the sperm-cell and germ-cell is a remark of Car- 
penter’s on the same point: 
“ Looking,” he says, “ to the very equal mode in which the characters 
of the two parents are mingled in hybrid offspring, and to the certainty 
that the material conditions which determine the development of the germ 
are almost exclusively female, it would seem probable that the dynamical 
conditions are, in great part, furnished by the male.”* 
§ 12. Could nothing but the foregoing indirect evidence be 
adduced in proof of the proposition that the spermatozoon is 
essentially a neural element, and the ovum essentially a haemal 
element, we should scarcely claim for it any thing more than 
plausibility. On finding, however, that this indirect evidence is 
merely introductory to evidence of a quite direct nature, its sig- 
nificance will become apparent. Adding to their weight taken 
separately the force of their mutual confirmation, these two series 
of proofs will be seen to give the hypothesis a high degree of 
probability. The direct evidence now to be considered is of 
several kinds. 
On referring to the description of the process of multiplication 
in monads, quoted some pages back (§ 5), from Professor Owen, 
the reader will perceive that it is by the pellucid nucleus that the 
growth and reproduction of these single-celled creatures are regu- 
lated. The nucleus controls the circulation of the plasmatic 
fluid; the fission of the ?iucleus is the first step toward the for- 
mation of another cell; each half of the divided nucleus estab- 
lishes round itself an independent current; and, apparently, it 
is by the repulsion of the nuclei that the separation into two 
individuals is finally effected. All which facts, when generalized, 
imply that the nucleus is the governing or co-ordinating part. 
Nowr, Professor Owen subsequently points out that the matter of 
* Trin. of Phys , p. 908. 32 
A NEW TIIEOItY OF POl'ELATION. 
the sperm-cell performs in the fertilized germ-cell just this same 
function which the nucleus performs in a single-celled animal. 
We find the absorption by a germ-cell of the contents of a sperm- 
cell “followed by the appearance of a pellucid nucleus in the 
center of the opaque and altered germ-cell; we further see its 
successive fissions governed by the preliminary division of the 
pellucid center;” and, led by these and other facts, Professor 
Owen thinks that “ one cannot reasonably suppose that the nature 
and properties of the nucleus of the impregnated germ-cell and 
that of the monad can be different.”* And hence he further 
infers that “the nucleus of the monad is of a nature similar to, if 
not identical with,” the matter of the spermatozoon. But wo 
have seen that in the monad the nucleus is the co-ordinating 
part; and hence to say that the sperm-cell is, in nature, identical 
with it, is to say that the sperm-cell consists of co-ordinating 
matter. 
Chemical analysis affords further evidence, though, from the 
imperfect data at present obtained, less conclusive evidence than 
could be wished. Partly from the white and gray nervous sub- 
stances having been analyzed together instead of separately, and 
partly from the difficulty of isolating the efficient contents of the 
sperm-cells, a satisfactory comparison cannot be made. Never- 
theless, possessing in common, as they do, one element, by which 
they are specially characterized, the analysis, as far as it goes, 
supports our argument. The following table, made up from data 
given in the Cyclopaedia of Anatomy and Physiology, Art. Nerv- 
ous System, gives the proportion of this element in the brain in 
different conditions, and shows how important is its presence: 
In 
In 
In 
In 
In 
Infants. 
Youth. 
Adults. 
OldMen. 
Idiots. 
Solid constituents in a hundred parts 
of brain 
Of these solid constituents the phos- 
17-21 
26 74 
27-49 
2616 
29 07 
phorus amounts to 
Which gives a per centage of phos- 
0-8 
1-65 
1-80 
100 
0-86 
phorus in the solid constituents of 
4 66 
6-41 
664 
3 82 
292 
* Purthonogencsis, pp. 66, 67. A NEW THEORY OF POPULATION. 
33 
This connection between the quantity of phosphorus present, 
and the degree of mental power exhibited, is sufficiently signifi- 
cant ; and the fact that in the same individual the varying de- 
grees of cerebral activity are indicated by the varying quantities 
of alkaline phosphates excreted by the kidneys,* still more clearly 
shows the essentialness of phosphorus as a constituent of nervous 
matter. Respecting the constitution of sperm-cells chemists do 
not altogether agree. One thing, however, is certain—that they 
contain unoxidized phosphorus; and also a fatty acid, that is not 
improbably similar to the fatty acid contained in neurine.f In 
fact, there would seem to be present the constituents of that ole- 
ophosphoric acid which forms so distinctive an element of the 
brain. That a large quantity of binoxide of protein is also present, 
may be ascribed to the fact that a great part of the sperm-cell con- 
sists merely of the protective membrane and its locomotive ap- 
pendage ; the really efficient portion being but the central contents.! 
Evidence of a more conclusive nature—evidence, too, which 
will show in what direction our argument tends—is seen in the 
marked antagonism of the nervous and generative systems. Thus, 
the fact that intense mental application, involving great waste of 
the nervous tissues, and a corresponding consumption of nervous 
matter for their repair, is accompanied by a cessation in the pro- 
duction of sperm-cells, gives strong support to the hypothesis 
that the sperm-cells consist essentially of neurine. And this be- 
comes yet clearer on finding that the converse fact is true—that 
undue production of sperm-cells involve cerebral inactivity. The 
first result of a morbid excess in this direction is headache, which 
may be taken to indicate that the brain is out of repair ; this is 
followed by stupidity; should the disorder continue, imbecility 
supervenes, ending occasionally in insanity. 
* Lectures on Animal Chemistry. By Dr. Bence Jones. Medical Timet, Sept. 13th, 
1851. See also Prin. of Phys., p. 171. 
t Cycloptedia of Anatomy and Physiology, vol. iv., p. 506. 
| From a remark of Drs. Wagner and Leuckart this chemical evidence seems to have 
nlready suggested the idea that the sperm-cell becomes “ metamorphosed into the cen- 
tral parts of the nervous system.” But though they reject this assumption, and though 
the experiments of Mr. Newport clearly render it untenable, yet none of the facts latterly 
brought to light conflict with the hypothesis that the sperm-cell contains unorganized 
co-ordinating matter. 34 
A NEW THEORY OF POPULATION. 
That the sperm-cell is co-ordinating matter, and the germ-cell 
matter to be co-ordinated, is, therefore, an hypothesis not only 
having much a priori probability, but one supported by numer 
ous facts. 
§ 13. This hypothesis alike explains, and is confirmed by 
the truth, that throughout the vertebrate tribes the degree of 
fertility varies inversely as the development of the nervous 
system. 
The necessary antagonism of Individuation and Reproduction 
docs indeed show itself among the higher animals, in some de- 
gree in the manner hitherto traced; namely, as determining the 
total bulk. Though the parts now thrown otF, being no longer 
segments or gemma?, are not obvious diminutions of the parent, 
yet they must be really such. Under the form of internal fission, 
the separative tendency is as much opposed to the aggregative 
tendency as ever; and, other things equal, the greater or less 
development of the individual depends upon the less or greater 
production of new individuals or germs of new individuals. As 
in groups of cells, and series of groups of cells, we saw that there 
was in each species a limit, passing which the germ product 
would not remain together; so in each species of higher animal 
there is a limit, passing which, the process of cell-multiplication 
results in the throwing off of cells, instead of resulting in the for- 
mation of more tissue. Hence, taking an average view, we see 
why the smaller animals so soon arrive at a reproductive age, 
and produce large and frequent broods; and why, conversely, 
increased size is accompanied by retarded and diminished fer- 
tility. 
But, as above implied, it is not so much to the bulk of the 
body as a whole, as to the bulk of the nervous system, that 
fertility stands related among the higher animals. Probably, 
indeed, it stands thus related in all cases; the difference simply 
arising from the fact, that whereas in the lower organisms, where 
the nervous system is not concentrated, its bulk varies as the 
bulk of the body, in the higher organisms it does not do so. Be 
this as it may, however, we see clearly that, among the verte- 
brata, the bodily development is not the determining circum- 
stance. In a fish, a reptile, a bird, and a mammal of the same A NEW THEORY OF POPULATION. 
35 
weight, there is nothing like equality of fecundity. Cattle and 
horses, arriving as they do so soon at a reproductive age, are 
much more prolific than the human race, at the same time that 
they are much larger. And while, again, the difference in size 
between the elephant and man is far greater, their respective 
powers of multiplication are less unlike. Looking in these cases 
at the nervous systems, however, we find no such discrepancy. 
On learning that the average ratio of the brain to the body is— 
in fishes, 1 to 5,668; in reptiles, 1 to 1,321; in birds, 1 to 212; 
and in mammals, 1 to 186 ;* their different degrees of fecundity 
are accounted for. Though an ox will outweigh half a dozen men, 
yet its brain and spinal cord are far less than those of one man; 
and though in bodily development the elephant so immensely 
exceeds the human being, yet the elephant’s cerebro-spinal sys- 
tem is only thrice the size attained by that of civilized men.f 
Unfortunately it is impossible to trace throughout the animal 
kingdom this inverse relationship between the nervous and re- 
productive systems with any accuracy. Partly from the fact 
that, in each case, the degree of fertility depends on three variable 
elements—the age at which reproduction begins, the number pro- 
duced at a birth, and the frequency of the births; partly from the 
fact that, in respect to most animals, these data are not satisfac- 
torily attainable, and that when they are attainable they are 
vitiated by the influence of domesticity; and partly from the 
fact that no precise measurement of the respective nervous sys- 
tems has been made, we are unable to draw any but general and 
somewhat vague comparisons. These, however, so far as they 
go, are in our favor. Ascending from beings of the acrite nerve- 
less type, which are the most prolific of all, through the various 
* Quain’s Elements of Anatomy, p. 672. 
t The maximum weight of the horse’s brain is 1 lb. 7 oz.; the numan brain weighs 3 
lbs , and occasionally as much as 4 lbs.; the brain of a whale, 75 feet long, weighed 5 lbs. 
5 oz.; and the elephant’s brain reaches from 8 lbs. to 10 lbs. Of the whale’s fertility we 
know nothing; but the elephant’s quite agrees with the hypothesis. The elephant 
does not attuin its full size until it is thirty years old, from which we may infer that it 
arrives at a reproductive age later than man does; its period of gestation is two years, 
and it produces one at a birth. Evidently, therefore, it is much less prolific than 
man. See Muller’s Physiology (Baly’s translation), p. 815, and Quain’s Elements of An- 
atomy, p. 671. 36 
A NEW THEORY OF POPULATION. 
invertebrate sub-kingdoms, among which spontaneous fission dis- 
appears as the nervous system becomes developed ; passing again 
to the least nervous and most fertile of the vertebrate series— 
Fishes, of which, too, the comparatively large-brained cartilagin- 
ous kinds multiply much less rapidly than the others; progressing 
through the more highly endowed and less prolific Reptiles to the 
Mammalia, among which the Rodents, with their unconvoluted 
brains, are noted for their fecundity; and ending with man and 
the elephant, the least fertile and largest-brained of all—there 
seems to be throughout a constant relationship between these 
attributes. 
And indeed, on turning back to our d priori principle, no other 
relationship appears possible. We found it to be the necessary 
law of maintenance of races, that the ability to maintain indi- 
vidual life and the ability to multiply vary inversely. But the 
ability to maintain individual life is in all cases measured by the 
development of the nervous system. If it be in good visceral or- 
ganization that the power of self-preservation is shown, this im- 
plies some corresponding nervous apparatus to secure sufficient 
food. If it be in strength, there must be a provision of nerves 
and nervous centers answering to the number and size of the 
muscles. If it be in swiftness and agility, a proportionate devel- 
opment of the cerebellum is pre-supposed. If it be in intelli- 
gence, this varies with the size of the cerebrum. As in all cases 
co-ordination of actions constitutes the life, or, what is the same 
thing, the ability to maintain life; and as throughout the animal 
kingdom this co-ordination, under all its forms, is effected by 
nervous agents of some kind or other; and as each of these nervous 
agents performs but one function, it follows that in proportion to 
the number of the actions co-ordinated must be the number of 
nervous agents. Hence the nervous system becomes the univer- 
sal measure of the degree of co-ordination of actions; that is, of 
the life, or ability to maintain life. And if the nervous system 
varies directly as the ability to maintain life, it must vary in- 
versely as the ability to multiply.* 
* That the rize of the nervou* system is the measure of the ability to maintain life, is 
a proposition that must, however, be taken with some qualifications. The ratio between A NEW THEORY Or POPULATION. 
37 
And here, assuming the constitution of the sperm-cell above 
inferred to be the true one, we see how the obverse a prior/ prin- 
ciple is fulfilled. Where, as among the lowest organisms, bulk 
is expi'essive of life, the antagonism of individuation and re-pro- 
duction was broadly exhibited in the fact that the making of two 
or more new individuals was the unmaking of the original indi- 
vidual. And now, among the higher organisms, where bulk is no 
longer the measure of life, we see that this antagonism is between 
the neural elements thrown off, and that internal neural mass 
whose bulk is the measure of life. The production of co-ordinat- 
ing cells must be at the expense of the co-ordinating apparatus; 
and the aggregation of the co-ordinating apparatus must be at the 
expense of co-ordinating cells. How the antagonism affects the 
female economy is not so clear. Possibly the provision required 
to be made for supplying nervous as well as other nutriment to 
the embryo, involves an arrest in the development of the nervous 
system; and if so, probably this arrest takes place early in pro- 
portion as the number of the coming offspring makes the required 
provision great: or rather, to put the facts in their right sequence, 
an early arrest renders the production of a numerous offspring 
pq§sible. 
§ 14. The law which we have thus traced throughout the ani- 
mal kingdom, and which must alike determine the different fertil- 
ities of species, and the variations of fertility in the same species, 
we have now to consider in its application to mankind. 
From the fact that the human race is in a state of transition, 
we may suspect that the existing ratio between its ability to 
multiply, and its ability to maintain life, is not a constant ratio. 
From the fact that its fertility is at present in excess of what is 
needful, we may infer that any change in the ratio will probably 
the amounts of gray and white matter present in each case is probably a circumstance 
of moment. Moreover, the temperature of the blood may have a modifying influence ; 
seeing that small nervous centers exposed to rapid oxidation will be equivalent to larger 
ones more slowly oxidized. Indeed, we see among mankind, that though, in the main, 
Bize of brain determines mental power, yet temperament exercises some control. There 
is reason to think, too, that certain kinds of nervous action involve greater consumption 
of nervous tissue than others; and this will somewhat complicate the comparisons. 
Nevertheless, these admissions do not affect the generalization as a whole, but merely 
prepare us to meet with minor irregularities. 38 
A NEW THEORY OF POPULATION. 
be toward a diminution of fertility. And from the fact that, on 
the whole, civilization increases the ability to maintain life, wo 
may perceive that there is at work some influence by which such 
diminution is necessitated. Before inquiring for this influence, 
let us consider what directions an increase of ability to maintain 
life may take—what scope there is for an increase. In some 
further development of the co-ordinating system, that is, in some 
greater co-ordination of actions, the increase must of course con- 
sist. But there are several kinds of co-ordination; and it will be 
well to ask of what kind or kinds increase is most requisite, and 
therefore most likely. For, doubtless, in conformity with the 
general law of adaptation, increase will take place only where it 
is demanded. 
Will it be in strength? Probably not. Though from pre- 
historic remains, we may gather that the race has become more 
bulky, yet the cause of this change seems now diminishing. Me- 
chanical appliances are fast supplanting muscular force, and will 
most likely continue to do so until they leave to be done by 
manual labor only as much as is needful for the healthy mainten- 
ance of the body at its then attained size. 
Will it be in swiftness or agility ? Probably not. In 
savage these form important elements of the ability to maintain 
life; but in the civilized man they subserve that end in quite a 
minor degree, and there seems no circumstance likely to necessi- 
tate an increase of them. 
Will it be in mechanical skill, that is, in the better co-ordination 
of complex movements? Most likely in some degree. Awkward- 
ness is continually entailing injuries and loss of life. Moreover, 
the complicated tools developed by civilization are constantly 
requiring greater delicacy of manipulation. Already the cerebel- 
lum, which is the nervous center directing compound motions, is 
larger in man than in any other creature except the elephant; and 
the daily-increasing variety and complexity of the processes he 
has to perform, and the appliances he has to use, may be expected 
to cause a further growth of it. 
Will it be in intelligence? Largely,no doubt. There is ample 
room for progress in this direction, and ample demand for it. 
Our lives are universally shortened by our ignorance. In attain- A NEW THEORY OF POPULATION. 
39 
ing complete knowledge of our own nature, and of the nature of 
surrounding things—in ascertaining the conditions of existence to 
which we must conform, and in discovering means of conforming 
to them under all variations of seasons and circumstances—we 
have abundant scope for intellectual culture, and urgent need for 
intellectual development. 
Will it be in morality, that is, in greater power of self-regula- 
tion 1 Largely, also; perhaps most largely. Normal conduct, or 
in other words, conduct conducive to the maintenance of perfect 
and long-continued life, is usually come short of more from defect 
of will than of knowledge. To the due co-ordination of those 
complex actions which constitute human life in its civilized form, 
there goes not only the prerequisite—recognition of the proper 
course; but the further prerequisite—a due impulse to pursue that 
course. And on calling to mind our daily failures to fulfill often- 
repeated resolutions, we shall perceive that lack of the needful 
desire, rather than lack of the needful insight, is the chief cause 
of faulty action. A further endowment of those feelings which 
civilization is developing in us—sentiments responding to the re- 
quirements of the social state—emotive faculties that find their 
gratifications in the duties devolving on us—must be acquired 
before the crimes, excesses, diseases, improvidences, dishonesties, 
and cruelties, that now so greatly diminish the duration of life, 
can cease. 
But whether greater co-ordination of actions take place in any 
or in all of these directions, and in whatever degree or proportions, 
it is clear that, if it take place at all, it must be at the expense 
of fertility. Regarded from the abstract point of view, increased 
ability to maintain life in this case, as in all others, necessarily 
involves decreased ability to multiply. Or, regarded in the con- 
crete, that further development of the co-ordinating system, 
which any advance pre-supposes, implies further decrease in the 
production of co-ordinating cells. 
§ 15. That an enlargement of the nervous centers is going on 
in mankind, is an ascertained fact. Not alone from a general 
survey of human progress—not alone from the greater power of 
self-preservation, shown by civilized races, are we left to infer 
such enlargement; it is proved by actual measurement. The 40 
A NEW THEORY OF POFULATION. 
mean capacities of the crania in the leading divisions of the species 
have been found to be— 
In the Australian 76 cubit inches. 
“ African 82 “ 
“ Malayan 86 “ 
“ Englishman 96* “ 
showing an increase in the course of the advance from the savage 
state to our present phase of civilization, amounting to nearly 30 
per cent, on the original size. That this increase will be contin 
uous, might be reasonably assumed ; and to infer a future decrease 
of fertility would be tolerably safe, were no further evidence 
forthcoming. But it may be shown why a greater development 
of the nervous system must take place, and why, consequently, 
there must be a diminution of the present excess of fertility ; and 
further, it may be shown that the sole agency needed to work out 
this change is—the excess of fertility itself 
For, as we all know, this excess of fertility entails a constant 
pressure of population upon the means of subsistence; and, as 
long as it exists, must continue to do this. Looking only at the 
present and the immediate future, it is unquestionably true that 
if unchecked, the rate of increase of people would exceed the rate 
of increase of food. It is clear that the wants of their redundant 
numbers constitute the only stimulus mankind have to a greater 
production of the necessaries of life; for, were not the demand 
beyond the supply, there would be no motive to increase the 
supply. Moreover, this excess of demand over supply, and this 
pressure of population, of which it is the index, cannot be eluded. 
Though by the emigration that takes place when the pressure 
arrives at a certain intensity, a partial and temporary relief may 
be obtained, yet, as by this process all habitable countries must 
gradually become peopled, it follows, that in the end the pressure, 
whatever it may then be, must be borne in full. 
But this inevitable redundancy of numbers—this constant in- 
crease of people beyond the means of subsistence—involving as 
it does an increasing stimulus to better the modes of produciug 
food and other necessaries—involves also an increasing demand 
* Lecture by Professor Owen, before the Zoological Society, Nor. 11th, 185L A NEW THEORY OF POPULATION. 
41 
for skill, intelligence, and self-control—involves, therefore, a con- 
stant exercise of these, that is—involves a gradual growth of 
them. Every improvement is at once the product of a higher 
form of humanity, and demands that higher form of humanity to 
carry it into practice. The application of science to the arts is 
simply the bringing to bear greater intelligence for satisfying our 
wants; and implies continued increase of that intelligence. To 
get more produce from the acre, the farmer must study chemis- 
try—must adopt new mechanical appliances—and must, by the 
multiplication of tools and processes, cultivate both his own 
powers and the powers of his laborers. To meet the require- 
ments of the market, the manufacturer is perpetually improving 
his old machines, and inventing new ones; and by the premium 
of high wages incites artisans to acquire greater skill. The daily 
widening ramifications of commerce entail upon the merchant a 
need for more knowledge and more complex calculations; while 
the lessening profits of the ship-owner force him to employ 
greater science in building, to get captains of higher intelligence, 
and better crews. In all cases, increase of numbers is the efficient 
cause. Were it not for the competition this entails, more thought 
would not daily be brought to bear upon the business of life; 
greater activity of mind would not be called for; and develop- 
ment of mental power would not take place. Difficulty in 
getting a living is alike the incentive to a higher education of 
children, and to a more intense and long-continued application in 
adults. In the mother it induces foresight, economy, and skillful 
housekeeping; in the father, laborious days and constant self- 
denial. Nothing but necessity could make men silbmit to this 
discipline, and nothing but this discipline could produce a con- 
tinued progression. The contrast between a Pacific Islander, all 
whose wants are supplied by Nature, and an Englishman, who, 
generation after generation, has had to bring to the satisfaction of 
his wants ever-increasing knowledge and skill, illustrates at once 
the need for, and the effects of, such discipline. And this being 
admitted, it cannot be denied that a further continuance of such 
discipline, possibly under a yet more intense form, must produce 
a further progress in the same direction—a further enlargement of 
the nervous centers, and a further decline of fertility. 42 
A NEW THEORY OF POPULATION. 
And here it must be remarked, that the effect of pressure of 
population, in increasing the ability to maintain life, and decreas- 
ing the ability to multiply, is not a uniform effect, but an average 
one. In this case, as in many others, Nature secures each step 
in advance by a succession of trials, which are perpetually re- 
peated, and cannot fail to be repeated, until suocess is achieved. 
All mankind in turn subject themselves more or less to the dis- 
cipline described; they either may or may not advance under 
it; but, in the nature of things, only those who do advance under 
it eventually survive. For, necessarily, families and races whom 
this increasing difficulty of getting a living which excess of fer- 
tility entails, does not stimulate to improvements in production 
—that is, to greater mental activity—are on the high road to 
extinction; and must ultimately be supplanted by those whom 
the pressure does so stimulate. This truth we have recently seen 
exemplified in Ireland. And here, indeed, without further illus- 
tration, it will be seen that premature death, under all its forms, 
and from all its causes, cannot fail to work in the same direction. 
For as those prematurely carried off must, in the average of 
cases, be those in whom the power of self-preservation is the 
least, it unavoidably follows, that those left behind to continue 
the race are those in whom the power of self-preservation is the 
greatest—are the select of their generation. So that, whether the 
dangers to existence be of the kind produced by excess of fer- 
tility, or of any other kind, it is clear, that by the ceaseless exer- 
cise of the faculties needed to contend with them, and by the 
death of all men who fail to contend with them successfully, 
there is insured a constant progress toward a higher degree of 
skill, intelligence, and self-regulation—a better 00-ordination of 
actions—a more complete life. 
§ 1G. There now remains but to inquire toward what limit 
this progress tends. Evidently, so long as the fertility of the 
race is more than sufficient to balance the diminution by deaths, 
population must continue to increase; so long as population 
continues to increase, there must be pressure on the means of 
subsistence; and so long as there is pressure on the means of 
subsistence, further mental development must go on, and further 
diminution of fertility must result. Hence, the change can never A NEW THEORY OF POPULATION. 
43 
cease until the rate of multiplication is just equal to the rate of 
mortality ; that is, can never cease until, on the average, each pair 
brings to maturity but two children. Probably this involves that 
each pair will rarely produce more than two offspring; seeing that 
with the greatly increased ability to preserve life, which the 
hypothesis presupposes, the amount of infant and juvenile mor- 
tality must become very small. Be this as it may, howrever, it 
is manifest that, in the end, pressure of population and its accom- 
panying evils will entirely disappear; and wrill leave a state of 
things which will require from each individual no more than a 
normal and pleasurable activity. That this last inference is a 
legitimate corollary will become obvious on a little consideration. 
For, a cessation in the decrease of fertility implies a cessation 
in the development of the nervous system; and this implies that 
the nervous system has become fully equal to all that is de- 
manded of it—has not to do more than is natural to it. But that 
exercise of faculties which does not exceed what is natural con- 
stitutes gratification. Consequently, in the end, the obtainment 
of subsistence will require just that kind and that amount of 
action needful to perfect health and happiness. 
Thus do we see how simple are the means by which the great- 
est and most complex results are worked out. From the point 
of view nowr reached, it becomes plain that the necessary antag- 
onism of individuation and reproduction not only fulfills with 
precision the a priori law of maintenance of race, from the monad 
up to man, but insures the final attainment of the highest form 
of this maintenance—a form in which the amount of life shall be 
the greatest possible, and the births and deaths the fewest pos- 
sible. In the nature of things the antagonism could not fail to 
W'ork out the results we see it working out. The gradual dimi- 
nution and ultimate disappearance of the original excess of fer- 
tility could take place only through the process of civilization; 
and, at the same time, the excess of fertility has itself rendered 
the process of civilization inevitable. From the beginning, press- 
ure of population has been the proximate cause of progress. It 
produced the original diffusion of the race. It compelled men to 
abandon predatory habits and take to agriculture. It led to the 
clearing of the earth’s surface. It forced men into the social 44 
A NEW THEORY OF POPULATION. 
state; made social organization inevitable; and has developed the 
social sentiments. It has stimulated to progressive improve- 
ments in production, and to increased skill and intelligence. It is 
daily pressing us into closer contact and more mutually depend- 
ent relationships. And after having caused, as it ultimately 
must, the due peopling of the globe, and the bringing of all its 
habitable parts into the highest state of culture—after having 
brought all processes for the satisfaction of human wants to the 
greatest perfection—after having, at the same time, developed 
the intellect into complete competency for its work, and the feel- 
ings into complete fitness for social life—after having done all 
this, we see that the pressure of population, as it gradually 
finishes its work, must gradually bring itself to an end. 
THE END. 7r PUBLISHED BT . 
FOWLERS AND WELLS, 
NO. 131 NASSAU STSEET, NEW YOKE. 
American Phrenological Journal and Miscel- 
lany. Devoted to Phrenology, Physiology, and Self-Improvement. A year, $1 00 
Amativeness; or, Evils and Remedies of Ex- 
cessive and Perverted Sexuality, with Advice to the Married and Single,- 12£ 
Accidents and Emergencies. By Alfred 
Smee. Illustrated. Every family should have it, . .... 12 J 
Botany for all Classes; containing a Floral 
Dictionary, with numerous Illustrations. By John B. Newman, M.D., - 50 
Bulwer and Forbes on the Water Treatment. 
Edited, with Additional Matter, by R. S. Houghton, M.D., SO 
Constitution of Man, considered in Relation 
to External Objects. A new, revised, enlarged, and illustrated edition, • SO 
Combe’s Lectures on Phrenology. By George 
Cambe. A complete course as delivered in the United States, • - X 00 
Combe on Infancy ; or, the Physiological and 
Moral Management of Children. Illustrated. An important work, - 50 
Chemistry, Applied to Physiology, Agricul- 
ture, and Commerce. By Prof. Liebig. With additions by Dr. Gardiner, 20 
Curiosities of Common Water. With Addi- 
tions by Joel Shew, M.D. From the fifth London edition of 1723, • . 23 
Cholera: Its Causes, Prevention and Cure; 
and all other Bowel Complaints, treated by Water, ..... 25 
Combe’s Physiology, Applied to the Improve- 
ment of Mental and Physical Education. New edition, with Notes, . 50 
Chart for Recording various Developments. 
Designed for Phrenologists. With numerous engravings, ... 
Constitution of Man. School Edition. By 
George Combe. Arranged with Questions, for a Class-Book, • • - 25 
Consumption, its Prevention and Cure, by 
the Water Treatment, with directions. Illustrated, 50 
Chronic Diseases, Especially the Nervous 
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Defence of Phrenology. By Dr. Andrew 
Boardman. A good work for skeptics and unbelievers, .... 50 2 
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Education Complete. Embracing Physiology, 
Animal and Mental, Self-Culture, and Memory, in one large volume, - 2 00 
Education, Founded on the Nature of Man. 
By Dr. Spurzhaim. A scientific work, with illustrations, . . - 50 
Elements of Animal Magnetism ; or, Process 
and Practical Application for relieving human suffering, .... 12J 
Errors of Physicians and Others, in the Ap- 
plication of the Water-Cure. By J. II. Rausse, 25 
Experience in Water-Cure, in Acute and 
other Diseases, with directions to patients, 25 
Familiar Lessons on Phrenology and Physi- 
ology. Muslin, in one volume. Beautifully illustrated, - - - - I 00 
Familiar Lessons on Phrenology. Designed 
for the use of Children and Youth, illustrated, ...... 50 
Familiar Lessons on Physiology. Designed 
for the use of Children and Youth, with engravings, 25 
Fascination ; or, the Philosophy of Charming. 
(Magnetism.) Illustrating the Principle* of Life. Illustrated, 40 
Food and Diet: Containing an Analysis of 
every kind of Food and Drink. By Professor Pereira, .... 50 
Familiar Lessons on Astronomy. Designed 
for Children and Youth in Schools and Fumilies. Beautifully Illustrated, 40 
Hereditary Descent: Its Laws and Facts ap- 
plied to Human Improvement New edition, illustrated, .... 50 
Human Eights, and their Political Guaran 
ties : Founded on the Moral and Intellectual Laws of our Being, - 50 
Home for All; or, a New, Cheap, Convenient, 
and Superior Mode of Building, with appropriate Diagrams, 50 
Hydropathic Encyclopedia. A Practical Sys- 
tem of Hydropathy and Hygiene. Illustrated. Ey R. T. Trail, M.D. - 2 00 
Hydropathy for the People. An excellent 
work on health. With Notes by Dr. Trail, 50 
Introduction to the Water-Cure. With an 
Exposition of the Human Constitution. By T. L. Nichols, M.D., - • 12J 
Love and Parentage: applied to the Improve- 
ment of Offspring, including important Directions to the Married, • • 25 
Lectures on the Philosophy of Mesmerism 
and Clairvoyance. With instruction in its process and practical application, 25 
Labor: Its History and Prospects. Including 
the Use and Abuse of Wealth. By Robert Dale Owen, .... 25 
Lectures on Hygiene and Hydropathy. By 
R. 8. Houghton, M.D., • M FOWLERS ASL WELLS’S PUBLICATIONS. 
3 
Maternity; or, the Bearing and Nursing of 
Children, including Female Education. With appropr. ate Engravings, • 50 
Marriage . Its History and Philosophy, with 
a Phrenological Exposition of the Functions for Happy Marriages, - • 37^ 
Memory and Intellectual Improvement: Ap- 
plied to Self-Education and Juvenile Instruction. Twentieth edition, - 50 
Mesmerism in India. A superior work, by 
the celebrated Dr. Esdaile. Highly recommended by professional men, - 50 
Matrimony; or, Phrenology and Physiology 
applied to the Selection of congenial Companions for Life, - - - 25 
Moral and Intellectual Science. By Combe, 
Stratton, Cox, Gregory, and others. Illustrated with Portraits, - - 2 00 
Natural Laws of Man, physiologically con- 
sidered. By Dr. Spurzheim. A work of great merit, 25 
Psychology, or the Science of the Soul. With 
Engravings of the Nervous System. By Joseph Haddock, M.D., • • 25 
Physiology of Digestion. The Principles of 
Dietetics. Illustrated with Engravings. By Andrew Combe, M.D., - 25 
Phrenology Proved, Illustrated, and Applied. 
Embracing a concise Elementary View of Phrenology, with a Chart - 1 00 
Phrenological Guide. Designed for the Use 
of Students of their own Characters. With numerous Engravings, - 12J 
Phrenological Almanac : Illustrated with nu- 
merous Engravings—containing illustrated descriptions of character, * 64 
Popular Phrenology, exhibiting the Phreno- 
logical Developments of more than fifty different Personages, 25 
Power of Kindness; Inculcating the Christian 
Principles of Love and Benevolence. An excellent work, 25 
Physiology, Animal and Mental: Applied to 
the Preservation and Restoration of Health of Body and Mind, - • 50 
Phrenology and the Scriptures, showing their 
Harmony. By Rev. John Pierpont, -------- 12A 
Principles of the Human Mind. Biology: in- 
cluding the Voltaic Mechanism of Man, 25 
Philosophy of Electrical Psychology. By 
John Bovee Dods, - 50 
Philosophy of Spiritual Intercourse: an Ex- 
planation of Modern Mysteries. By Andrew Juckson Davis, - - - 50 
Beligion, Natural and Revealed ; or, the 
Natural Theology and Moral Bearings of Phrenology, .... 50 
Self-Culture and Perfection of Character; 
including the Management of Youth. Improved stereotyped edition, • 50 4 
FOWLERS AND WELLS’S PUBLICATIONS. 
Science of Swimming: Giving the History 
of Swimming, with special Instruction to Learners. Illustrated, . • 12} 
Sober and Temperate Life: With Notes and 
Illustrations by Comaro, who lived 154 years. Head this Book, • • 25 
Synopsis of Phrenology and Physiology: Il- 
lustrating the Temperaments. Designed for Phrenologists and others, • 12} 
Temperance and Tight-Lacing: Founded on 
the Laws of Life as developed by Phrenology and Physiology, * - 12} 
Tobacco: Its Effect on the Body and Mind. 
The best work oa the subject. Every body should read it, - • • 25 
The Use of Tobacco; Its Physical, Intellect- 
ual, and Moral Effects on the Human System, ...... 12} 
Teeth; Their Structure, Disease, and Man- 
agement, with the Causes of Early Decay. Full of Engravings, - - 12} 
Thoughts on Domestic Life. Its Concord 
and Discord, with Suggestions to both Sexes. By Nelson Sizer, • • 12} 
Tea and Coffee ; Their Physical, Intellectual, 
and Moral Effects on the Human System, 12} 
The Parent’s Guide, and Childbirth made 
Easy ; with Advice to Mothers. By Mrs. Pendleton, .... 50 
The Illustrated Self-Instructor in Phrenology 
and Physiology ; with One Hundred Engravings and a Chart, • - 25 
Vegetable Diet, as Sanctioned by Medical 
Men, and Experience in all ages; also a System of Vegetable Cookery, * 50 
Water-Cure Library; Embracing all of Im- 
portance on the Subject. In seven largo 12mo volumes, • • * 5 00 
Water and Vegetable Diet in Scrofula, Can- 
cer, Asthma, and many other Diseases. By Dr. Lamb, • • • • 50 
Water-Cure Manual; A Popular Work on 
Hydropathy. With familiar Directions. Every family should have it, • 50 
Water-Cure Almanac, Containing much im- 
portant matter for all classes. Published yearly, ..... 6} 
Woman: Her Education and Influence. With 
a General Introduction, by Mrs. Kirkland. With thirteen Portraits, • 40 
Water-Cure Journal and Herald of Reforms. 
Devoted to Hydropathy and Medical Reform. Circulation 25,000. A year, 1 00 
Water-Cure for Women in Pregnancy and 
Childbirth. Illustrated with numerous cases. A good work, • - • 25 
Water-Cure in Every Known Disease. By 
J. H. Rausse. Translated by C. H. Meeker, from the German, - • 50 
All Works on Phrenology, Physiology, Mag- 
netism, Physiognomy, Phonographv, tho Water-Cure, or Hydropathy, 
may be obtained of Foweebs and WELD a, 131 Nassau Street, New York. HYDROPATHIC ENCYCLOPEDIA: 
3 Idfrunjilrte ftjstnn nf Injiinijintlni null 33tjgim. 
An Illustrated Work. In Two large 12mo Volumes. 
Embracing Outlines of Anatomy. Illustrated ; Physiology of the Human Body; 
Hygienic Agencies, and the Preservation oe Health ; Dietetics and Hydro- 
pathic Cookery; Thkoky and Practice of Water-Treatment; Special Pathol- 
ogy and IIydro-Therapkutics. including the Nature, Causes, Symptoms, and 
Treatment oe all known Diseases; Application to Surgical Diseases; Appli- 
cation of Hydropathy to Midwifery and the Nursery; with a Glossary, Ta- 
ble of Contents, and complete Index. 
Published by Fowlers and Wells, New York and Boston. Price for the complete Work, 
substantially Bound in Embossed Muslin, lettered on the back in library style, $2 50. 
That our country friends who have not seen this great work, may judge of 
its merits and practical utility, we herewith present a few brief 
BY R . T. TR ALL, M.D. 
“ The Hydropathic Encyclopedia.” The 
title of the book does no justice to the extent 
and variety of the information which it con- 
tains. In preparing it, no pains have been 
spared in collecting and consulting the most 
valuable authorities. For popular reference, 
we know of nr. work which can fill its place. 
Without any parade of technical terms, it is 
strictly scientific; the language is plain and 
simple ; the points explained are of great im- 
portance ; devoted to progress, the editor is 
no slave to theory; he does not shock the 
general reader by medical ultraisms ; while 
he forcibly demonstrat -s the benefits of mod- 
ern improvements. Of all the numerous pub- 
lications which have obtained such a wide 
popularity, as issued by Fowlers and Wells, 
perhaps none are more adapted to general 
utility than this rich, comprehensive, and 
well-arranged Encyclopedia.—AT. Y. Tribune. 
Every family, whether in tavor of hydrop- 
athy or not, should have the information em- 
bodied in this work.—Democratic Standard. 
A volume of great beauty, as well as an aux- 
iliary of incalculable value in every house- 
hold.—Montgomery Watchman. 
Certainly a more useful work has not been 
issued hy these really useful publishers.— 
Williamsburgh Daily Times. 
There is a strong vein of common sense run- 
ning through the work, and its extensive cir- 
culation will be a public benefit.—Old Colony 
Memorial. 
Another good work on the right subject.— 
Hartford Daily Times. 
Every page is replete with practical and 
useful instruction.—Boston Ledger. 
NOTICES OF THE PRESS. 
It is a work of medical ability, so popular- 
ized as to be comprehended and practiced by 
the people. It acquaints the reader with man- 
ifold things that pertain to life, health, and 
happiness.—N. Y Reformer. r 
The IlvnnopATntc Encyclopedia will be 
exceedingly useful as n family guide and text- 
book, and is published at a very low price, 
considering its size, illustrations, and intrin- 
sic value.—N. Y. Former and Mechanic. 
Hydropathic advocates will here find the 
proper information in the several departments 
of learning necessary, not only to a particular 
system but to all systems.—Aberdeen Courier. 
For those who desire to understand the hy- 
dropathic system in its practical operations, it 
will be invaluable.— Concord Democrat. 
It possesses great value.—Ch. Ambassador. 
All who wish to learn the science of preserv- 
ing hea'th by the most simple means, should 
send for it at once.—Perrysoille Eagle. 
Few works more indispensable to the hu- 
man family have ever been Issued from tho 
American press.—Madison County Journal. 
Full of scientific and useful information. It 
should be in the hands of every one, both in 
and out of the medical profession.— Troy Times 
Were its directions acted upon, we should 
not hear such frequent complaints of dyspesia 
and weak nerves.— The Metropolitan. 
Much useful information concerning the 
laws of life may be derived from this work 
for the people.—Union Journal. 
A work that the learned m-iy be proud to 
possess.—Literary Journal. 
The most valuable work of reference on the 
Water-Cure.—ConneaulviUe Courier. 
Published at the Office of the Water-Cure Journal in Clinton Hall, 
BY FOWLERS AND WELLS, 
Bouton, 142 Washington St. j 
New York, 131 Na*aa« Street