1 88 Outline of Genetics 



these overripe eggs to be fertilized, and the resulting 

 progeny were loo per cent males. His conclusion was 

 that sex was not determined by the chromosome equip- 

 ment, but by the physiological conditions of the egg, 

 high water content resulting in males. 



This theory was confirmed in a striking way in 191 2 

 by Miss King (15), who performed the converse of 

 HERT^VEG's experiments, using toads' eggs. Taking 

 some newly laid eggs, she withdrew^ water from them; 

 then allowed them to be fertilized, and the resulting 

 progeny were 90 per cent females. The obvious conclu- 

 sion is that eggs with low water content produce females. 



Finally, there is the remarkable work of Riddle (18) 

 with pigeons. Hertweg and Miss King had found that 

 sex is determined by the physiological factor of water 

 content. Riddle has investigated the matter a little 

 more fully, and from his analysis of the physiological 

 conditions of male and female he gives the following 

 contrasts : 



Male Female 



High percentage of water Low percentage of water 



Low percentage of fat High percentage of fat 



Low percentage of phosphorus High percentage of phosphorus 



High rate of metabohsm Low rate of metaboUsm 



It appears from this that high water, low fat, and low 

 phosphorus are male attributes or conditions, while the 

 female attributes are the reverse. The main feature of 

 difference, however, to which the other contrasting con- 

 ditions are subordinate, is that the male shows high 

 metabolism and the female low metabolism. The idea 

 is that any physiological conditions that affect water 

 content, fat content, or phosphorus content, or through 



