THE SEX RATIO IN THE DOMESTIC FOWL.^ 



By RAYMOND PEARL. 



(Read April 13. 1917.) 



I. Introduction. 



One of the most notable biological discoveries of recent years is 

 that which has demonstrated the cytological mechanism of sex de- 

 termination. As a result of the work of McClung, Wilson, Stevens, 

 Montgomery, Morgan, and many other investigators, we have a 

 tolerably clear understanding of the cellular mechanism by which it 

 is determined, in a wide variety of forms, that particular individuals 

 are males while others are females. At first sight it would appear 

 that the discoveries referred to had made superfluous further studies 

 of sex ratios. The whole history of the statistical investigation of 

 sex ratios, viewed from the standpoint of present knowledge of the 

 mechanism of sex determination, seems a rather futile and blind 

 groping after something which very successfully eluded that form 

 of pursuit. 



But there are still reasons, as it seems to the writer, why it is 

 desirable to carry on certain sorts of statistical investigations of sex 

 ratios. The most important of these is that there is a considerable 

 body of evidence in the literature, which would seem to show, if 



1 Papers from the Biological Laboratory of the Maine Agricultural Ex- 

 periment Station. No. iig. This paper constitutes No. VIII. of a series 

 of " Sex Studies " by the present writer. 



It was originally intended that this should be a much more extended 

 paper than it now is. When it was presented before the Society a number of 

 matters were discussed which do not appear here at all. This condition of 

 affairs arises from the fact that in the midst of the preparation of the final 

 manuscript for the printer the writer was called to war work which made 

 impossible the completion of the paper in the form originally contemplated. 

 In view of the impossibility of foretelling when the writing could be com- 

 pleted it seemed desirable to publish the portion already done rather than to 

 leave the whole till the somewhat uncertain time of the end of the war. 



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