322 



riddle: control of sex ratio 



fied ratios. And since it has now been shown (we shall here 

 attempt to demonstrate the point) that a real reversal or con- 

 trol of sex has been effected in these forms, the large and dimor- 

 phic ova found generally in doves and pigeons have permitted 

 new lines of investigation on the nature of sex itself. As a final 

 result of these studies — a result that we may very briefly indi- 

 cate in advance of the presentation of the data — we believe that 

 it is now reasonably clear that the two sexes are in fact the 



TABLE 1 

 On the Relation Between "Width of Cross" and the Sex Ratio 



expression of the rate of protoplasmic activity — of metabolism — 

 pitched at two different heights or levels. For the pigeon world 

 the data seem quite conclusive, and when we shall have reviewed 

 a part of these data we will undertake to place before you the 

 experimentally modified sex ratios obtained elsewhere among 

 animals, in an attempt to show that this considerable body of 

 evidence supplies further confirmation, and only confirmation, 

 for the modifiability of sex, and for our conclusion that the male 

 sex is an expression of metabolism at a higher level, the female 

 sex of metabolism at a lower or more conservative level. 



