T1IK AMPIII1UA. 



65 



position of the future longitudinal axis of the body of the chick. 

 Soon, the lateral boundaries of this groove, in what will become 



, a 



J 



Fig. 31. 



Fig. 31. — Development of the Chick. 



A. First rudiment of the embryo ; a, its cephalic ; 6, its caudal end ; c, primitive groove. 



B. The embryo further advanced; a, b, c, as before; d, the dorsal laminae developed in 



the cephalic region only, and nearly uniting in the middle line; e, the proto -vertebra;. 



C. Letters as before. The dorsal laminae have united throughout the greater part of the 



cephalic region, and are beginning to unite in the anterior spinal region. 



D. Embryo further advanced (second day), the dorsal laminae having united throughout 



nearly their whole length. The proto- vertebrae have increased in number, and the 

 omphalo-meseraic veins,/, are visible. 

 The embryos are drawn of the same absolute length, but it will be understood that the 

 older embryos are, in nature, longer than the vounrer. 



F 



