4o8 



ON INCREASE IN SIZE 



[PT. Ill 



shown in Fig. 45. And the growth-rate per gram of embryo (Minot 

 growth-rate divided by 100?) was also proportional to the amount 

 of yolk remaining. 



Gray himself indicated a number of criticisms which might be 

 brought against his views. Thus there is little a priori reason for sup- 

 posing that the growth-rate of the embryo should be determined by 

 the amount of yolk in the yolk-sac, for apart from anything else, the 



10 



20 30 40 50 60 70 

 Fig. 45. Days of development. 



80 90 100 



amount and nature of the syncytium in the yolk-sac wall might be 

 a limiting factor. One would also expect that in the beginning when 

 the yolk is very large compared to the embryo, the yolk would be 

 present in excess, and would not exert any influence on growth-rate. 



2-7. The Autocatakinetic Formulae 



The workers mentioned so far might be divided into three groups, 

 those who have elaborated empirical formulae, those who have 

 adopted the Minot point of view, and those who have treated the 



