472 



J. B. JOHNSTON 



Fig. 81 Pig embryo, 50 mm. Rapid development of the anterior pallial com- 

 missure has produced a condition very similar to that of the adult bat. The 

 commissure still occupies the lamina supraneuroporica but also extends forward 

 from its dorsal border to form a crescent. Above the crescent is seen the indu- 

 sium in a condition very much like that of the hippocampal formation in the 

 opossum or bat. I can find no indication of secondary fusion. The rostral limb 

 of the commissure is formed simply by the invasion and stretching of the dorsal 

 border of the lamina supraneuroporica by additional corpus callosum fibers. 



