INDEX 



655 



Yolk sac, roof of, in chick, 80, 8 1 

 in Mammals, 85 

 in man, 87 

 stalk, loo, 107, 137, 317 



Zander, concerning the nails, 439 

 Ziegler, concerning malformations of neural 

 tube, 607 



Ziegler's fusion theory of symmetrical duplic- 

 ity, 599 

 Zona pellucida, n, 34, 409 



radiata, 409 

 Zonula Zinnii, 578 

 Zonular placenta, no 

 Zygomatic bone, 194 

 Zymogen granules, 354 



