SECT, i] PHYSICO-CHEMICAL SYSTEM 249 



salicylate, may here be mentioned. Starting out from this practical 

 suggestion the work led to the discovery of a number of specific 

 effects of substances such as quinine on egg size and yolk size. Thus 

 Riddle & Basset found that alcohol markedly reduces yolk size in 

 pigeons, Riddle & Anderson found that quinine reduces egg size, 

 yolk size and albumen size but has no effect on the protein/fat ratio 

 of the egg, while Behre & Riddle found that the diminution of 

 albumen size under quinine bore more on the solids than on the 

 water and involved considerable reduction of the protein. 



The elaborate investigations on the egg of the tern, already 

 mentioned, led to a significant correlation between abundance of 

 food and size of egg, and it is certain that the size of the hen's egg is 

 affected by its diet since the work of Atwood. There seems also to be 

 a seasonal fluctuation, the weight of the eggs increasing from July 

 to February and decreasing from March to June. These seasonal 

 fluctuations appeared distinctly in Atwood's data, and explain the 

 results of Curtis and of Fere. Rice, Nixon & Rogers and Riddle 

 found a definite relation between the amount of food consumed and 

 the number of eggs produced, both of these factors varying exactly with 

 the seasonal variation in the egg size. Fluctuations of a regular kind 

 seem even to occur each month, according to Hadley who observed 

 such changes in egg weight and number. According to Curtis the size 

 of the eggs increases as the laying bird matures, in the case of the hen, 

 and Pearson has observed similar variations in the case of the sparrow. 



The genetics of egg production have been studied by Pearl and 

 Benjamin. 



The relation between the egg weight and the chick weight at 

 hatching has been studied by Halbersleben & Mussehl and by 

 Iljin. The former workers found a quite consistent relation within 

 one breed between the weight of the egg before incubation and the 

 weight of the chick at hatching, the latter averaged 64 per cent, of 

 the former. After thirty-five days of post-natal life, however, the 

 slight advantage possessed by the chicks from the heavier eggs had 

 altogether disappeared. They also noted that, other things being equal, 

 chicks hatched from the more pigmented eggs (browner) weighed 

 slightly more than those hatched from the less pigmented ones. 

 Abnormally large and abnormally small eggs did not hatch as well 

 as those of medium weight. Iljin collected a great many figures but 

 his text contains no statistical analysis. 



