UPON 
MERISMATIO MULTIPLICATION 
IN SOME 
ANNELIDA. 
[From the American Journal of Science and Arts, Vol. XXXV, Jan., 1863.J Upon Natural and Artificial Section in tome Chcptopod, Annelids. 
BY W. C. MINOK. 
The circumstances of spontaneous fission have been observed 
in so few species of annelids at present, as to make every additional 
observation of value, even though only confirmatory of what is 
already known upon that subject. This consideration, and the 
fact that all views of its nature in the Oligochcetu seem to be based 
upon the observations of one species—Stylaria proboseidea,—have 
tempted me to publish the following brief investigations, how- 
ever they may want of auy very special novelty to give them 
value. 
It is now nearly one hundred years since the distinguished 
Danish naturalist, Otto Fr. Muller, studied the phenomena of 
spontaneous fission in the fresh water Naids,1 and his able little 
work, Von Wurmen des sussen und salzigen Wassers, Kopenhagen, 
1771, largely devoted to that subject, shows that he failed only 
where the imperfect means at his command led him astray. 
The multiplication by artificial section had been observed before 
that, both in the Naids and other animals, and had awakened a 
good deal of general interest; but the multiplication by sponta- 
neous fission seems to have been very nearly if not wholly dis- 
regarded at that time. Nor has its occurrence in the fresh water 
worms received, since then, the investigation that it seems to de- 
mand. For with the exception of a discussion by Schultze and 
Leuckart upon some of the particulars, and, the significance of 
this phenomenon in relation to budding, some ten years ago, and 
a sweeping denial of its occurrence, or at least of its vital and 
systematic nature, by Dr. Williams, about the same time, no 
one, so far as I am aware, has published any extended observa- 
tions upon the fissiparity of the fresh water Naids since the time 
of Muller.2 And yet the statements of Dr. Williams, in regard 
to both artificial and spontaneous fission, are such as to suggest 
at once the importance of a reexamination of the whole subject; 
while the great interest given to this question by the remarkable 
speculations of Steenstrup, together with the interesting varie- 
ties of the phenomenon as observed in the marine worms by 
1 Trembley had discovered it long before this, as he observes in his Memoires 
p. s. a l’hist. dun genre de Polypes d'eau douce, 1744;—and Roesel, in his Insekten 
belustigungen, describes the united parent and bud; but the former did no more 
than observe the fact, and the latter wholly misunderstood what he saw. 
2 Gruithuisen remarks in his Anntomie der gezungelten Naide, (Nov. Act. Nat. 
Cur. T. xi, p. 243,) only that it is uncommon to find a Naid without buds of the 
second generation, aud refers to Muller for the details of their formation. Since 
writing this, 1 have seen in Leuckart’s valuable yearly report in the Archiv. f. Na- 
turgeschichte for 1861, a notice of Claus’s observations on fission iu Chatogaster, 
which, so far as there given, I can confirm. 36 
W. C. Minor upon Fission in some Annelids. 
Quatrefages, Edwards, Frey and Leuckart and others, seem to 
demand a more complete knowledge than we as yet possess of 
its occurrence in the fresh water group, 
I may here remark that the European species chiefly studied 
hitherto, Stylaria proboscidea, has not come under my observation, 
nor am I aware that it has been found in America. Four spe- 
cies of Naids common in this vicinity, Stylaria (Pristina) longi- 
seta, Nais rivulosa, and Dero limosa, found in fresh water, and a 
marine Enchytroeus, E. triventralopeclinatus, have been the prin- 
cipal subjects of my investigation. In regard to the first of 
these, it may be questioned whether our species is identical with 
that described by Ehrenberg, (Symbolce Physical,) as Pristina 
longiseta, for his description is too brief to be of specific value. 
As, however, the characters given by D’Udekem, in his Nouvelle 
Classification des Annelides Setigeres Abranches, (Memoires de VAcad. 
Royale de Belgique, 1859, T. xxxi,) apply equally to the Ameri- 
can species, I am compelled to regard it as the same.3 The 
second species, Nais rivulosa, already described by Leidv, (Jour- 
nal Acad. Nat, Sci. Phila., 1850, vol. ii, pt. 1°, p. 43,) very closely 
resembles the European Nais elinguis, with which D’Udekem 
regards it as identical. The third species, Dero limosa, has 
also been described by Leidv, (Proc. Acad. Phila., 1857, vol. v, 
p. 226) and though overlooked by D’Udekem, appears to be dis- 
tinct from the European form of the same genus. The fourth, 
Enchytroeus triventralopeclinatus, I have not been able to identify 
with any species described in works at my command, and have 
therefore named from the three anterior pairs of ventral combs 
after which the dorsal combs begin. This character appears to 
distinguish it from E. socialis, if I may judge from the figure 
given by Leidy {Jour. Acad. Phila.). It has no eyes. The pharynx 
extends nearly to the fourth ventral or the first dorsal combs, 
from which a narrow esophagus continues to a little back of the 
sixth ventral combs. Here a gradual enlargement of the ali- 
mentary canal occurs, ending abruptly just back of the eighth, 
in a narrow twisted tube; and this last gradually enlarges, at the 
ninth ventral combs, into a moderate sized alimentary canal, in 
3 D’Udekem remarks : “ Je n’ai pas adopts le genre Stylaria adinis par Lamarck 
et Ehrenberg, paree que cette espece ne differe ties autres Nais que par l’allonge- 
inent grand de la levre Ce charact&re n’dtant accompagne d’aucnne 
modification importante dans la form des autres organes, je ne puis le eonsiderer 
comme assez tranche pour servir a former un genre nouveau.” There is however a 
marked difference in the form and position of the cordiform anterior enlargement of 
the alimentary canal, which even the statements and figures of Muller and Gruithu- 
isen indicate, between the Naids with a long upper lip or proboscis and those 
with a short one, and the manner of fission differs in these two groups as will be 
shown. Lamarck’s genus Stylaria is therefore a good one. Ehrenberg’s division 
of this genus however, based upon the absence of eyes, is unfounded, for I have 
seen Nais rivulosa lose them without any other apparent change, and Agassiz has 
stated that this occurs as a part of the normal development in many Naios. TV. C. Minor upon Fission in some Annelids. 
37 
which I observed nothing specially marked. The entire length 
of this Naid was about f inch. 
The occurrence of spontaneous fission in Stylaria (ISTais) pro- 
boscidea is described as follows by Muller. “If a virgin jSTaid, 
as I may call it, with 16 or more pairs of hair combs or 20 or 
more pairs of hook combs [there are four pairs of hook combs 
anterior to the first hair or dorsal combs as in N<ais and Dero\ 
be carefully observed it will be seen that its anal ring slowly 
elongates and after some days appears to be transversely marked 
within into rudiments of future rings.4 In each of these divis- 
ions beneath the skin, germs of hooks and hairs appear, and the 
pulsations of the artery are evident, while the food forces a way 
through them. The hooks and hairs gradually come through 
the skin in succession from before backward, while the rings en- 
larging, the Naid increases considerably in length. While in 
this way new segments and their contents are forming within 
the anal ring, on the other side [anteriorly] of it, a strongly 
marked transverse line, different from those just mentioned, ap- 
pears, and extends across the whole width of the animal. The 
angles formed at the sides of the body project, and on the top a 
slight projection is evident which gradually becomes a distinct 
proboscis, while, finally, eyes appear back of this fission. Thus 
the Naid becomes a mother.” . . . “Frequently one may see in 
the anterior half of the elongated anal ring of the mother Naid 
a second ring formation similar to the one just described.” . . . 
“ This is not all. Hardly has the second bud acquired the length 
of one mature ring than a third bud appears before it, and I have 
even seen a fourth.” . . . “Further, not only may a parent and 
its four offspring thus appear, but the buds themselves may give 
rise to new buds; their terminal joints forming new buds as they 
themselves were formed. Hence we may find a parent with its 
children and grand-children attached to its body.” (op. cit. pp. 
34, 36.) 
Muller afterwards gives his observations upon a single Naid 
from the 20th of May to the 9th of June. During this time, it 
gave off the buds observed posterior to the 17th pair of combs, 
after which a formation of rings began, without any trace of 
separation, until the body was elongated to over 40 pairs of 
combs. About this time a fission occurred between the 21st 
and 22nd pairs of combs. Fission occurring in this way after 
an elongation of the body I shall speak of as the “renewal of 
fission.” Further observation of individual Naids led him to 
4 Schultze considers Muller in error as to the position at which fission takes place, 
because he describes it as occurring in a segment and not between two. The differ- 
ence of statement however is simply verbal, as Muller speaks of “ die Zwischen- 
Raume der Borsten oder die Gelenke,” p. 26, and in many other places shows very 
plainly that such is his meaning. 38 
W. C. Minor upon Fission in some Annelids. 
conclude that each bud is formed one joint anterior to its prede- 
cessor, that there is thus a gradual reduction of the parent seg- 
ments till a certain point; that then a reformation of rings 
takes place, and an elongation of the body of the Naid to re- 
commence this circle of fission. 
Schultze, in his article, Uber die Fortpflanzuvg durch Theilung 
bei Nais proboscidea (Archiv f. Naturgeschichte, 1849, T. xv, p. 
293,) confirms the statements of Muller as to the passage over 
of one of the parental segments to each bud;5 though he is not 
fortunate enough to observe the recommencement of fission in 
the elongated Naid. He observes also (p. 301) that, contrary to 
what Steenstrup had supposed from the analogy of marine 
worms, there is no relation to metagenesis in the phenomena of 
budding in this Naid, for he had never seen generative organs 
in the separated buds. He had however never been able to keep 
these buds long alive. He also had seen (p. 304,) sexual organs 
in the parent while budding, though he had never seen well de- 
veloped sperm and ripe eggs present during this process. 
The phenomena of fission in Stylaria longisela, so far as I have 
observed them, confirm the statements of Muller and Schultze 
in substance ; for there is nearly always a passage over of one 
parental ring to each bud, and since fission takes place, as I have 
seen, while the parent has eggs and sperm, and I have never 
seen the fullest development of the latter in th& buds, I cannot 
believe that there is any such metagenetic relation in this pro- 
cess as has been observed in Sgllis and allied genera. 
In Nais rivulosa, however, the facts are somewhat different. 
For in several continued observations of individual Naids, ex- 
tending in one case over twelve weeks, I have known, but once 
or twice of a passage of the parental rings into the bud; while, 
after an elongation of the parent body, I have very uniformly 
seen fission recommence in the point at which buds were given 
off before, or at some point posterior to it, and once anterior, 
and finally, although I have seen fission taking place between 
each of the rings from the 15th to the 22d, I have not been able 
to discover that it does so in any order. But here, as in Stylaria 
longiseta, I have found no metagenesis in the fission. 
The facts obtained in regard to fission in Dero limosa are un- 
fortunately meagre; the comparative slowness of the meris- 
matic function making the only two series of observations car- 
ried out proportionately unfruitful. In none however of the 
succeeding buds, from Aug. 15th to Oct. 10th, was there any 
carrying off of parental segments by the separating parts, nor 
was there anything like metagenesis observed. 
5 Leuckart at first doubted the correctness of this view, (Ub<:r die ungeschlccht- 
liche Vermehrung bei Nais proboscidea, Wiegm. Arch. 1857,) but has since been 
convinced of its justice. W. C. Minor upon Fission hi some Annelids. 
39 
My observations upon Enchytrceus triventralopectinatus are sim- 
ilarly scanty, but are just sufficient to confirm and extend the 
facts observed in the two other short-lipped Naids. In all the 
cases observed, the separation was of a part wholly new formed, 
without inclusion of the older segments of the parental body. 
It is evident from the above facts, that in Stylaria longiseta, as 
Muller and Schultze have shown is the case in S. proboscidea, the 
point of fission moves regularly forward, ring by ring, and more 
commonly in the former Naid from the 16th to the 12th pairs of 
hook combs; though the extremes between which I have known 
it to occur are the 17th and 10th. To judge from Muller’s ac- 
count it occurs further back in the latter Naid. Further, that 
in Nats rivulosa, and. as far as I know, in Dero limosa, and in En- 
chytrceus triventralopectinatus, all of which have short upper lips, 
the buds are given off at one point, though that point may vary 
in different Naids of the same species, or in one and the same 
Naid at different times. In the latter case the variation occurs 
as part of a peculiar form of fission of which I shall speak again. 
Both “parting” (theilung), and “budding” (knospenbildung), 
occur then in the Naids, and it may be added that the former 
appears to be peculiar to the genus Stylaria or to the proboscis- 
bearing forms. 
I may here remark that the distinction made by Schultze and 
others between “theilung” and “knospenbildung,” though con- 
venient, does not seem to me a fundamental one. The mere in- 
clusion of a portion of parental tissue in the bud does not of 
itself make an essential distinction between this and a wholly 
new-formed, but otherwise similar, bud; nor have I been able 
to see any histological or functional differences. The very fact 
that individuals, having the same genetic relations to the parent 
stock, are in one Naid, N. rivulosa, always or commonly pro- 
duced by the so-called “budding,” and in another genus, Stylaria, 
by the so-called “parting,” leads to this view. Nor, as I think, 
though observations are largely wanting in that direction, have 
the two yet been shown to be functionally different in true meta- 
genetic processes. They are two varieties of one process; and it 
would be interesting in many ways to know exactly how the 
various species of Naids, already known, follow distinctly the 
one or the other plan, or tend to merge them yet more com- 
pletely as one.6 
A little detail will show how closely identical the two forms of 
bud-formation are. In “parting”—“theilung”—as has already, 
to a great extent, been described by Schultze, we find that from 
6 I have known “budding” to intercalate once in a series of fissions in Stylaria 
longiseta (May 31), and I have also known “parting” to interrupt a series of bud- 
dings in Nais rivulosa (Sept. 25), which leads me to expect that in some Naids 
both processes may be regularly present. TV. C. Minor upon Fission in some Annelids. 
40 
the parental ring, as a fixed point, there is a continuous ring-form- 
ation and elongation backward; and that anteriorly to it there is 
a limited elongation of the general body, also by ring-formation 
from before backwards. There is, then, unlimited growth back- 
ward from the fixed point, and a limited or defined growth back- 
ward toward the fixed point from the place of fission. The pa- 
rental included ring, the most anterior of the series, is here the 
fixed point. In “budding”—“knospenbildung”—the most ante- 
rior ring of the series also, though a wholly new-formed one, be- 
comes the fixed point, from which, by continuous ring-formation, 
the Naid elongates backward, and toward which a limited series 
of ring-formations proceed from the point of fission.7 The resem- 
blance between the two is perfect; and as the fixed point is not 
related to specializations of the alimentary tube, as I at first sup- 
posed, and is in Stylaria proboscidea, where it occurs by “parting,” 
four hook-combs back of the mouth, as it is in Nats and Dero, 
where it occurs by budding, while in S. longiseta it is six hook- 
combs back, the genetic relations of the two processes, in these 
genera at least, are completely one. But, as I have already said, 
though the distinction appears unessential in the genera I have 
examined, the terms are convenient and as merely descriptive 
terms are used here. 
The “ commencement of fission” was observed in a large pro- 
portion of the buds given off from the individuals of Stylaria 
and Nais which were under observation, and the result is given 
in the following table. 
Stylaria—between 12-13 combs in none. 
13- “ 2 
14- “ 12 
15- “ 9 
16- “ 1 
Nais—between 17-18 combs in 3 
18- “ 3 
19- “ 4 
20- “ 3 
21- “ 3 
It is evident that fission does not begin at a fixed point, nor 
have I been able to discover any relation between the place of 
its occurrence and the time of the year, temperature, &c. 
Now, while fission may take place by gradual reduction of the 
Naid Stylaria, between the 10th and 11th hook-combs, the com- 
mencement of fission has not been known forward of the 13th. 
In Nais rivulosa, also, fission has been observed as far forward as 
the 15-16th, while its commencement has not been noted ante- 
rior to the 17th hook-combs. This is all the difference between 
the commencement of fission and continued fission, notwith- 
7 There is an interesting analogy between this process in the Hauls and the em- 
bryonic growth of Terebella, as described by Milne Edwards. He has remarked, 
Obs. sur le developpcment des Annelides, Ann. des Sci. Nat., 1845, 8me S6rie, T. iii, 
that the first defined part is not the cephalic, nor the anal, but the esophageal, and 
that growth tabes place both anterior and posterior to this by succession from 
before backward. Other speculations and analogies suggest themselves here, but 
are in our present knowledge wholly premature. W. C. Minor upon Fission in some Annelids. 
41 
standing the fact that whether the former is introductory to a 
series of “partings” or of “buddings,” its bud resembles that 
produced by what I shall call the “renewal of fission.” 
That the “renewal of fission,” in a Naid elongated after re- 
duction by fission, is a somewhat peculiar form of Hssion would 
hardly have been known from observations on Slylaria alone.8 
The following summary will illustrate this. In Slylaria longiseta 
one example (April 16) was reduced to 10 rings, grew out but 
little, and divided between the 12-13th. When again reduced 
to 10 rings it grew out much longer but renewed fission at the 
same point as before. It was then reduced to 11 rings, and 
growing out, again divided between the 12-13th. One of its 
buds (May 14) began fission between the 15-16th, was reduced 
to 12 rings, then grew out and recommenced fission between the 
14- and was being reduced again when lost. In another 
case, the Naid was reduced to 12, grew out and renewed fission 
at the 14-15th, was again reduced to 12, and growing out again 
renewed fission at the same point. It was a third time reduced 
to 12, and growing out again, a third time, renewed fission be- 
tween the 14-15th hook-combs. It was then reduced to 11, 
when very unfortunately lost. In Nais rivulosa, an example, 
that had been giving off buds just back of the 19th ring, in- 
creased to something like 33, and then again renewed fission be- 
tween the 19-20th. Another example that had given off’ buds 
at the 15th, grew out to over 35, and then renewed fission at the 
15- After two or three buds had been given off, it again 
elongated, and then renewed fission between the 20-21st hook- 
combs. 
Now, while in Slylaria the “ renewal of fission ” appears to 
differ from the commencement of fission, with which I believe 
it is essentially homologous, only by not occurring as far back, 
which may be owing to the want of fuller observation, and while 
in this genus it might be supposed to be merely a means of con- 
tinuing the process of “parting,” which must otherwise soon 
cease: we find that it occurs in Nais rivulosa without any change 
of the point of budding, without any apparent necessity, without 
performing the very function that we might judge from Stylaria 
was its peculiarity. And what is more, it also occurs in Nais 
rivulosa for the performance of this very function. This fact 
suggests something more than a physiological meaning in the 
“renewal of fission.” While the phenomena connected with it 
seem to show that the distinction between this, the “renewal of 
fission,” and other forms of fission is more than a difference of 
function, I am far from claiming that there is any fundamental 
8 Yet Muller seems to notice these two forms of fission, and says that “though 
at first view different they are fundamentally the same.” Op. cit. s. 38. 
Am. Jour. Sci.—Second Series, Vol. XXXY, Xo. 103.—Jant., 1863. 42 
IK C. Minor upon Fission in some Annelids. 
difference, like that between metagenetic and monogenetic fis- 
sions. I may add that I have not been able to discover that the 
point of its occurrence bears any relation to the number of buds 
already given off.9 
The sum of the preceding observations tends to show, that 
the “renewal of fission” has some special characters that suggest 
a wider enquiry as to its true nature; that the two forms of fis- 
sion already known as “parting” and “budding” both occur in 
the Naids, and occur so as to prove their morphologic and physi- 
ologic identity; that “ parting” appears to characterize the Naids 
with a prolonged upper-lip—the genus Stylaria, while “budding” 
appears to characterize those with a short one—AJais, Dero, En- 
chytrceus, and Chcetogaster, according to Claus; that the bud pro- 
duced by both these processes is identical with the parent; that 
as the buds are here, so far as I know, identical with their pa- 
rents in function and structure, there is no metagenetic fission ; 
and that therefore fission in these Naids, whether by “parting” 
or by “budding,” is correlative to genesis in the great function 
of maintenance of the species, and not a mere step in the his- 
tory of the individual.19 
It may be worth while to refer briefly here to the power of 
reproduction from injuries commonly attributed to these little 
beings, especially as Dr. Williams, in his Report on the British 
Annelida, {Rep. Brit. Ass. Adv. Sci., 1851, p. 247), after quoting a 
summary of Bonnet’s well known experiments, says: “On the 
authority of hundreds of observations, laboriously repeated at 
every season, the author of this report can declare with deliber- 
ate firmness, that there is not one word of truth in the above 
statement.” It may be presumed from this, that Dr. Williams felt 
the necessity of thorough and very careful investigations, before 
contradicting the statements so often repeated upon this subject; 
and I cannot doubt that his experiments have uniformly failed. 
9 There are some other differences to be considered in a future paper upon the 
histologic nature of fission. 
10 “From the analogy of the two species, Arenicola and Nais, on which the au- 
thor’s observations have been chiefly conducted, the conclusion may be deduced that 
the ‘fission of the body’ in every other species of Annelida in which it occurs has for 
object in like manner to protect and incubate the ova.” . . . “It becomes the last 
act of the parental worm, since the portions into which the body is sub-divided by 
fission never take food" . . . “ It is a catastrophe, in which every autumn involves 
the whole community.”—Williams, Rep. Brit. Annel., pp. 249-250. 
1 should be far from wishing to extend the conclusions I have made to all other 
Annelids by mere analogy, but my observations are, at least, wholly incompatible 
with a general application of Dr. Williams’s statements to the Naids. 
The exact circle of life and its duration, I have not determined, nor do I feel cer- 
tain that any of the general statements—see Leidy, Flora and Fauna within living 
animals, on Stylaria fossularis, and Williams at large—are absolutely correct. For 
I have known the process of fission to go on in winter, when the Naids were kept 
in a warm place: while I have also seen, what appeared to be a loss of this power, 
as shown in badly formed and incomplete buds, occurring in the warmer parts of 
the year. TV. C. Minor upon Fission in some Annelids. 
43 
But from the almost uniform success of my own, I should won- 
der that they have done so, had not others reported complete or 
partial failures in similar experiments.—See I)uges, Ann. des Sci. 
1828, lre Serie, T. xv. It must be remembered, however, that 
such evidence is wholly negative, and cannot weigh with the posi- 
tive statements of observers like Miiller, Beaumur and Dugbs. 
In regard to my own observations, I may state, in brief, that 
in Stylaria, Nais, and Z)ero, I have hardly ever failed to have 
the head reproduced, and that the anal end has not only been 
reproduced in these genera, but I have seen it reproduced in En- 
chytneus, in Lumbricus, in Fabricia, and even in a Nereis common 
on our coast.11 That in the vast majority of these cases I have 
seen food taken again ; and, in all, I have seen the incurrent anal 
stream, which ceases while either end is closed, recommence. 
From these and other observations, I am inclined to believe that 
this power is far more general in the class than is yet supposed. 
That this power plays a part in the natural econom}'- of life, 
the healing fragments of Naids that I have found in our pools 
is a proof. When saved from the attacks of Chcetogaster, even 
the shortest, headless, and almost immovable, fragments may 
go on to as full a recovery as when preserved by the observer. 
In one instance, I found, Aug. 21st, what was apparently five seg- 
ments of some Naid’s trunk, the two ends of which had closed 
and elongated. This had been preserved for some time, for the 
sur esophageal brain was well formed anteriorly, and the germs 
of hook combs were well defined posteriorly. It went through 
a rapid growth, developed eyes about the 22nd, opened the 
newly formed mouth about the 23rd, was supplied with food, 
and growing long divided between the 15-16th hook-combs and 
then gave off 5 buds in succession at that point till Oct. 8th, 
when it was lost. 
The thin film with which the Naids line the jars in which they 
are kept may be seen to serve, there at least, as a protection 
against the attacks of the prowling carnivorous Chceiogasters, and 
once beneath this, a fragment, like the one just referred to, ma}r 
be preserved till the eyes and mouth are formed—a period usu- 
ally of a fortnight. And though we should hardly have expected 
a mere piece of five segments to be preserved as this was, even 
though endowed with the power of recovery, yet we cannot re- 
gard so extended and remarkable a function as this appears to 
be, as useless or inoperative in the natural course of Naid-life. 
11 Careless observations made a number of years ago led me to think that the 
Nereids are destitute of the power of recovery from injuries, and Williams states 
that they always sloughed away ring alter ring, in his experiments. Reaumur re- 
marks: “Les experiences que j’ai fait faire sur des millepieds de mer, d'une toute 
autre longeur. sur de ces millepieds longs de sept a lmit pouces, n’ont pas eu le meme 
succes: mais les essais n’ont peutetre pas ete encore assez i epet4s ni assez suivis.”— 
Mem. pour s. a rhist, des Insects, 1'. vi, p. 59. Thinking the latter statement very 
probable I retried the experiments during the past year, with more care, and in 
every case with success.