THE DEVELOPMENT OF THE EMBRYO ITSELF, 101 
“i Fie. 116, 
Fig. 115. 
Fig. 114.--Transverse section through lumbar region of an embryo at end of fourth day (Fos- 
ter and Balfour). nc, neural canal; pr, posterior root of spinal nerve with ganglion ; 
ar, anterior root; A. G. C, anterior gray column of spinal cord: 4. W. C, anterior white 
column in course of formation ; m. p, muscle-plate ; ch. notochord ; W. R, Wolffian ridge ; 
AO, dorsal aorta; v. c. a, posterior cardinal vein; W. d, Wolffian duct; W. b, Wolffian 
body, consisting of tubules and Malpighian corpuscles ; g. e, germinal epithelium ; d, ali- 
mentary canal; M, commencing mesentery ; SO, somatopleure ; SP, splanchnopleure ; 
V, blood-vessels ; pp, pleuroperitoneal cavity. 
Fig. 115.—Diagram of portion of digestive tract of chick on fourth day (after Gitte). The 
black line represents hypoblast ; the shaded portion, mesoblast ; lg, lung diverticulum, 
expanding ie bases into primary lung vesicle ; st, stomach ; I, liver ; p, pancreas. 
Fia. 116,—Head of chick of third day, viewed sidewise as a transparent object (Huxley). Ja, 
cerebral hemispheres ; Ib, vesicle of third ventricle; II, mid-brain ; III, hind-brain; a, 
optic vesicle ; g, nasal pit ; b, otic vesicle ; d, infundibulum ; e, pineal body ; h, notochord; 
, fifth nerve; VII, seventh nerve; VIII, united glossopharyngeal and pneumogastric 
nerves. 1, 2, 3, 4, 5, the five visceral folds. : 
