Arthur B. Lamb 



193 



The ninsculature arising from this somite is innervated by the 

 ■oculomotor. This nerve is diiTerentiated at an 8 mm, stage. It arises, 

 Neal, 98, from the ventral floor of the mid-brain, as processes from 

 neuroblast cells in the ventral horn of this encephalomere. It extends 

 backward to the ciliary ganglion and runs through it to the walls of 

 the 1st somite. Neal, 98, p. 22 T, found, at a stage before the appear- 

 ance of the oculomotor, processes extending from the ciliary ganglion 

 to the somite, similar to those found in connection with the anterior 



s c 



Fig. 5. — Reconstruction of optic vesicle anrl derivatives of the mandibular and 

 liyoid somites of tlie right side of an Acanthias embryo, 22 mm. long, viewed from 

 medial side. 



somite. As in that case, I have been unable to convince myself that 

 the fibres Avhich seem to connect ganglion and somite are really nervous 

 in character. 



Secoxd, oe M.vxD[BUL.\ii SoMiTE. — This somite is the largest in the 

 head, and is characterized by the possession of a visceral portion con- 

 necting it with the ventral ctelom. 



Hoft'mann. 96, found this somite marked off by constrictions frcnii 

 the general body cavity at a 20 somite stage. A contracted lumen was 

 present. At this stage the floor of the brain is pressed closely down 

 upon the notochord and somite, but as growth takes place it draws 



