298 



H. V. NEAL 



Fig. 3 A portion of a frontal section of a 13-min. Squalus embryo, showing 

 the nidulus of the oculomotor nerve in the floor of the midbrain vesicle (II). 

 The neuraxon processes of the neuroblast cells may be traced into the root of 

 the nerve (oc). 



Fig. 4 A portion of a cross-section of a Squalus embryo ('pup' stage) in the 

 regio'n of the optic lobes, showing the relations of the nidulus (nidl.oc.) of the 

 oculomotor in the floor of the brain. A compact bundle of axons may be traced 

 from the nidulus into one of the roots (oc.) of the nerve. The ganglion cells of 

 the oculomotor lie near the median ventral sulcus of the midbrain and appear to 

 be actuallj- nearer the ependyma than in the earlier stage shown in figure 3. 



