Iviii Journal of Comparative Neurology, 



It does not follow from the excessive development of the reces- 

 sus infundibuli in the amphibia that the axis has suffered a greater 

 flexure than in higher vertebrates. [May it not be suggested that the 

 greater development of the brain, while the axis of the jaws, and hence 

 of the cranial base, is retained in the vertebral plane, causes a flatten- 

 ing of the infundibular region which makes necessary a retro- 

 growth of the infundibular parts, thus producing a spurious flexure 

 scarcely homologous with the "hook-flexure" of higher brains. 

 Something similar exists in the later fishes.] 



In the base of the diencephalon and mesencephalon the follow- 

 ing parts are recognized : 



Within-tegmental eminence, recessus mammillaris, saccus vasculo- 

 sus, entrance to infundibulum, recessus infundibuli or rec. basilaris ; 

 on the outside-fossa supra-mammillaris, eminenta mammillaris, tuber 

 cinereum, infundibulum, field beneath the infundibulum and basilar 

 ridge. 



The discussion of the epiphysis seems to be an endless theme 

 and it is here that we are compelled to disagree with the distinguished 

 author in several particulars. 



He insists that epiphyses may develop from various segments of 

 the roof of the primitive fore-brain. Of course there may be wide 

 range of difference in the use of the term epiphysis, but assuredly no 

 fact is more capable of proof than than that the conarium or pineal 

 epiphysis is a structure sui generis and not to be compared with the 

 other projections of the fore-brain. Not to anticipate a paper now in 

 preparation by one of the writer's students, it may be simply stated 

 that in all groups of vertebrates the essential relations are identical. 

 Although Stieda and others have identified the projecting plexus (par- 

 aphysis) as the pineal in reptiles, all groups of reptiles agree in the 

 fact that the pineal proper arises from a point immediately caiidad of che 

 supracommissure and is essentially tubular. When it is largely devel- 

 oped it bocomes lobate, but even in Phrynosoma does not develop an 

 epiphysal vesicle distinct from the pineal as stated by Ritter. 



In birds it has a tubular lobate form in early stages and does not 

 entirely lose its character. In tailed Amphibia some of these lobes 

 appear to become distinct and form a flattened vesicle but this is a 

 spurious appearance or a retrograde process. 



The parietal nerve arises from the supra-commissure and passes 

 alongside the pineal, adhering to its cephalic aspect and can be traced 

 (in Fhrynosotna) to the parietal organ in the skull with complete cer- 

 tainty. The segment following the supra-commissure is often highly 



