THE 



AMERICAN NATURALIST 



Vol. L. July, 1916 No. 595 



SEX CONTROL AND KXOWX CORE ILLATIONS IN 

 PIGEONS 1 



Dr. OSCAR RIDDLE 

 Statiox for Experimental Evolution, Cold Spring Harbor, L. I., N. Y. 



When one nowadays states that he has obtained a real 

 control— a reversal— of the development of sex, he can 

 feel assured that his biological audience demands a very 

 large volume of rigid proofs. The first reason for this 

 large requirement is, as you well know, that the asser- 

 tion of sex control lias been often made, and that in most 

 of these cases the data have proved disappointing; in- 

 adequate in one or another respect. A second reason for 

 present widespread skepticism as to even the possibility 

 of a real control of sex-development centers in the now 

 well-demonstrated fact that in some groups of animals, 

 the male— and in other cases the female— produces sex 

 cells of two kinds when these are considered from the 

 standpoint of their chromosomal numbers or character- 

 istics ; and further that each of these two groups of germs 

 normally gives rise to organisms of the sex correspond- 

 ing to the chromosomal constitution of these germs. 

 Moreover, certain linkage phenomena observed in breed- 

 ing such forms, unquestionably show themselves to be 

 normally associated with these same chromosomal dif- 

 ferences. 



But the experimentalist has learned through some pre- 



1 Paper read before the American Society of Naturalists, Columbus, Ohio, 

 December 30, 1915. 



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