16 



between the fourth and sixth week. In general, however, they indicate 

 growth to the beginning of the fifth week (6 ram X 4,5 mm) after 

 which there is a slow and variable decrease, the smallest with "some" 

 glands being 5 mm X 2 mm for an embryo of approximately 43 days. 



L , Fig. 2 a. Photouiicrograph of transverse section of umbilical vesicle of 13 mm 

 embryo through region of greatest calibre, showing variations in thickness of wall and 

 character of the coagulum. In the apex above, in the bend to the right, and in the 

 lower bend to the left open tubules are seen. Original magnification 40 diam. Reduced 

 Vs in reproduction. Made by Dr. Leopold Jaches, Cornell University Medical Col- 

 lege, New York City. 



The dimensions of the only vesicle of a 13 mm embryo are given as 

 3,7 mm X 3 mm. The greatest dimensions of my sections taken 



