THE AMERICAN NATURALIST 



[Vol. L 



vious contests with ideas of fixity and causality that when 

 normal structural correlations have been demonstrated in 

 the field of development, nothing has been decided as 

 to causality and inflexibility; indeed it is commonly at 

 such a point that experiment applies the pressure of new 

 or unusual conditions and makes an approach toward 

 learning the nature of a phenomenon, by forcing the latter 

 to break from its normal correlations, and disclose some- 

 thing of its real nature through its versatility— through 

 its own capacity to shift from response to one set of 

 conditions, to response to another set of conditions. 

 Laws of causation, in the field of development, are not to 

 be deduced from studies concerning the normal associa- 

 tions of the structures of the cell; they may be approached 

 through demonstrations of the versatility and responsive- 

 ness under pressure of those processes native to living 

 matter. 



We have stated that when sex is controlled an audience 

 like this will demand a volume of proof. It is clear that 

 the time limits here do not admit so extensive a presen- 

 tation. I should like to note here, however, that Profes- 

 sor Whitman's complete studies on sex in doves and 

 pigeons have been prepared for publication, and for sev- 

 eral months have been in the hands of the publisher. 

 The results of my own studies of the past five years de- 

 signed to test the reality of the sex-control, and the na- 

 ture of sex, as exhibited in these forms, will already 

 doubtless fill another volume. And, since the last volume 

 of the posthumous works of Professor Whitman is near- 

 ing completion, I can promise that it will not be long be- 

 fore the work of preparing my own results for publica- 

 tion will be begun. Only when all of these data are fully 

 available to you, may we expect a judgment as to whether 

 the evidence for our thesis to-day is adequate. It is pos- 

 sible to give here, within the time limits, only an outline 

 of the kinds of study which have yielded evidence on the 

 question of sex-control in pigeons. 



These studies were begun, and carried on for many 

 years by Professor Whitman. He obtained indispu- 



