LATER DEVELOPMENT OF CHICK AND RABBIT 417 



bending of the front end of the embryo in such a manner that not 



c f ms 



mt 



CrSJ. 



MyelencJ. 

 au.P. 



3./0. 



frstr. 



B 



FIG. 146. A. Chick embryo -with twenty pairs of somites (45 hours), dorsal 

 view. B. Chick embryo with twenty-seven pairs of somites (48 hours), 

 viewed from above. From Kellicott, after Lillie. 



A. A . o.m. , vitelline artery ; au. P. .auditory pit ; Cr .Fl., cranial flexure ; D.C., ductus Cuvieri ; 

 Dienc., diencephalon ; mesenc., mesencephalon ; Metenc., metencephalon ; Myelenc., i and 2, 

 anterior and posterior divisions of the myelencephalon ; Op.Ves., optic vesicle ; Ph., pharynx ; 

 pr.str., primitive streak ; S2, 55, etc., second, fifth, etc., somites ; Telenc., telencephalon ; Vel.tr., 

 velum transversum ; Ven., ventricle. 



B. a., auricle ; am., posterior margin of amnionic folds ; c., carotid loop ; cf., cranial flexure ; 

 d., diencephalon ; d.C., ductus Cuvieri ; gi, g2, gs, first, second, and third gill clefts ; i., isthmus ; 

 /., lens ; ma., mandibular arch ; ms., mesencephalon; mt., metencephalon ; o., otocyst (aud:tory 

 sac) ; just to the right of the otocyst is a thickening representing the ganglion of the VII. and VIlJ. 

 cranial nerves ; r ., retinal layer ; S2, sio, sao, second, tenth, and twentieth somites ; t., tail-bud ; 

 v., ventricle; v.a., vitelline artery; v.v., vitelline vein; i, 2, 3, first, second, and third aortic 

 arches ; V '., ganglion of V. cranial nerve. 



only does the anterior end turn to the right, but the right side of the 



2 E 



