SECT. 2] 



AND WEIGHT 



395 



usual "normaltafeln", shows the first appearance of the primitive 

 groove at the loth hour of development, an assessment which is 

 agreed to by Jenkinson and by Foster & Balfour (12th hour). 



Table 53. Probable dimensions of egg-cells. 



"The general course of pre-natal growth in the mouse, the guinea- 

 pig and the chick, can be expressed by straight lines relating the 

 logarithms of the weight and the age only when age is counted from 

 the beginning of the embryo proper." Such is the conclusion of 

 McDowell and his collaborators, and, though it may seem barren 



