FROM TWELVE TO THIRTY-SIX SOMITES eA 
CELL: 
Ol. VeVi =~ Nim V. Mefenc. Is th. 
Fic. 99. — Entire embryo of 31 somites viewed as a 
transparent object. 
am. Umb., Amniotic umbilicus. B. a., Bulbus 
arteriosus. cerv. Fl., Cervical flexure. ch. Fis., Cho- 
roid fissure. er. Fl., Cranial flexure. D.C., Duct of 
Cuvier. ex. 0. c., External layer of the optic cup. 
int. o. c., Internal layer of the optic cup (retina.) 
N’m., Neuromere of myelencephalon. olf., Olfactory 
pit. pe. W., Line of attachment of amnion to peri- 
eardial wall. V.C.1, 2, 3, First, second, and third 
visceral clefts. Other abbreviations as before. 
