318 



VERTEBRATE ZOOLOGY 



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Fig. 163. — Chick embryo of 35 somites, drawii as a transparent object, a. a. 

 1, 2, S, 4, First, second, third, and fourtli aortic arches; Ar, artery; .1. V, vitelline 

 artery; cerv.Fl, cervical flexure; cr. /''/., cranial flexure; D.C, duct of Cuvicr; 

 Ep, epiphysis; Gn. V, ganglion of trigeminus; Isth, isthmus; Jug. e.r, external 

 jugular vein; Md, mandibular arch; M.M, maxiUo-mandibular branch of the 

 trigeminus; o/f. P, olfactory pit; Ophlh, ophthalmic branch of trigeminus; Ot, 

 otocyst; V, vein; 11'. 6, wing bud; 1'. C. p. posterior cardinal vein; V. uinh, um- 

 bilical vein; V. V, vitelline vein; 1'. ]'. />, posterior vitelline vein. (From Lillie's 

 " Development of the Chick.") 



