EMBRYO OF 6 MM. 



229 



cient for the identification of the parts. The otocyst is large and conspicuous, 

 and the arrangement of the nerves is essentially similar to what we find in the 

 older embryos. The neuromeres, however, are very distinct, especially those 



Vm.IV. 



A. car 



Ven.lir. 



Md. 



Fig. 134. — Pig, 6.0 mm. Transverse Series 9, Section 90. 

 A. car. Carotid artery. Jug, Jug' , Jugular vein. Md, Medullary wall of the fore-brain. N.i, N.2, N.j, N.4., 

 Neuromeres of the hind-brain. N.^, Trigeminal ganglion. N.y,8, Acustico-facial ganglion. N.g, Root 

 of the glosso-pharyngeal nerve. Ot, Otocyst. Ven.IIIy Third ventricle or cavity of the fore-brain. 

 Ven.IV, Fourth ventricle. X 35 diams. 



Upon the left side of the embryo, N. i, 2,j, 4. Of these, the third is perhaps 

 the most characteristic. Each neuromere is separated from its fellow by an 



