The Intra-Uterine Growth-Cycles of the Guinea-Pig. 



721 



Table VI. 



Per cent of weight gained or lost, during the period of gestation, 

 by five guinea-pigs which gave birth to dead, premature litters. 



that in which rabbits, mice, and rats are born. If such were the 

 case, the young must have been born before 50 days, for the two 

 cycles seem to join or overlap between 50 and 60 days. This period 

 seems to be a critical one in the development of the foetus. In- 

 spection of the weights of mothers which gave birth to dead young 



