416 



THE DEVELOPMENT OF THE CHICK 



(caudal sclerotome halves) beneath the notochord is known as 

 the subnotochordal bar (Froriep). It forms earlier than the 

 remainder of the body of the vertebra and during the membranous 

 stage is thicker, thus forming a ventral projection at the cephalic 

 end of the vertebral body that is very conspicuous (Fig. 235). 



1 i' i s * vi^ 







csud Se/ I 



Fig. 234. — Frontal section inckiding the same vertebral pri- 



mordia as Fig. 233, at a higher level through the neural arches. 



a. C, Anterior commissure of the spinal cord. v. R., Ven- 

 tral root of spinal nerve. Other abbreviations as before (Fig. 



232). 



It chondrifies separately from the vertebral body and earlier. 

 Except in the case of the first vertebra it fuses subsequently 

 with the remainder of the vertebral body, and disappears as 



