April 30, 1947
Dear Jacques:
I received your letter of the 19th of April and am indeed sorry that my previous letters have caused you such remorse and anguish for not having answered them.  Please set your mind at ease since I did not expect very rapid answers in any case.
I am indeed sorry to hear of the troubles that you have had during this last winter and hope sincerely they are all over now.  I am not at all surprised to hear of your re-entrance into political activity once more.  I should think it would be a difficult thing to keep out of in France these days.
With reference to certain of the questions which you have asked, I shall try to answer them as well as I can.  I am sending under separate cover the Science article reprint which you probably have seen but of which you do not have copy.  In addition, I am sending several manuscripts on papers which I have sent in.  It so happens that I am now engaged almost exclusively in writing up the material which has accumulated in the last two years and as I finished each paper, I will send a copy out to you.  My review article I have been postponing until I have finished writing up some of the original material.  I have been so extremely busy with the transformation problem during the year that I did no writing until the last month.
The transformation has been one of the most exasperating problems that I have ever worked on and even yet is not in a completely satisfactory state.  We have been able to transform tagged strains into galactose fermenters.  We have repeated it now about twenty-five times.  The strain is tagged and we are absolutely certain that we are dealing with a transformation, since we are in this way sure that the strain we end up with is the strain with which we started the experiment.  The unsatisfactory part of the experiment is that the method of making the active principle is as yet not completely controlled.  We have a method now which gives us active preparations about 70% of the time and we are still looking for the cause of the failures.  We have recently gotten several important leads, we think, and if they work out, I think part of the problem will be solved.  I shall probably write up a preliminary note soon to send in to Nature, and will send a copy to you immediately.
With reference to my European trip, I am afraid that your plan is not workable.  I will not have enough money to take a plane and so will not be able to arrange to return to America with you.  As a matter of fact I have not as yet gotten all the money together even to go by boat.  I have been waiting to hear from Ephrussi who has been trying to get Needham to supplement the grant I got from Stockholm.  If something does not come through soon I have have to give up the entire idea.
Thus far, my plan, if everything turns out all right, is to arrive in Paris about the last week in June, just as you suggest, and to remain there until I go to Stockholm, and then, after the Copenhagen meetings and the meeting in Oxford, I plan to return to Paris for a few more weeks, and then go back to America at the end of August.
Give my fond regards to Andre and to Boris, if you see him.  Hoping to see you soon,
Sincerely yours,
S. Spiegelman