BM 



PD 



FIG. 12. A. SAGITTAL SECTION OF EMBRYO SHOWN IN FIG. u, 



D, SHORTLY BEFORE THE CLOSURE OF THE BLASTOPORE. (After 



Marshall.) 



B, blastopore. B F, fore-brain. B //, hind-brain. BM. mid-brain. //, 

 entoblast. L, liver. M, mesoblast. M N, mesenteron. N, notochord. jVC, 

 neurenteric canal. /", beginning of pituitary body as in growth of ectoblast. 

 P ' D, proctodaeum. K, rectal diverticulum of mesenteron. S, central canal of 

 spinal cord. F, yolk-cells. 



B. SAGITTAL SECTION OF EMBRYO SHOWN IN FIG. u, E, SHORTLY 



AFTER THE CLOSURK OF THE BLASTOPORE. (After Marshall.) 



Bfi\ fore-br^in. BH, hind-brain. B M, mid-brain. CH, notochord. M, 

 mesoblast. A" C, neural tube. N T, neurenteric canal. P N, pineal body. PT. 

 pituitary body. TV, intestinal region of mesenteron. T P, pharyngeal region of 

 mesenteron. U, proctodaeal or cloacal opening. W^ liver. K, yolk-cells. 



33 



