86 EMBEYOLOGY OF THE LOWEK VEETEBEATES ch. 



The side wall of the hind-brain now comes to project outwards as 

 a prominent knob while the side wall of the fore-brain also bulges out- 



Fig. 51. — Brain of young Lepidosiren as seen from the dorsal side. 



A, stage 31+ ; B, stage 35- ; C, stage 38 ; D, adult. c.H, cerebral hemisphere ; n.a, neural arch ; 

 pin, pineal body; rh., rhombencephalon; thai, thalamencephalon ; t.o, tectum, opticum. I, II, etc., 

 cranial nerves. [Figs. A and B are more highly magnified than C, and Fig. C than D.] 



wards — the bulging in this case being the rudiment of the cerebral 

 hemisphere (Fig. 51, A, c.H). 



The portion of the primitive fore-brain lying just in front of the 

 transverse fold of the brain-floor is the infundibulum. Farther 

 forwards the inner surface of the brain-floor forms a transverse 



