92 Journal of Comparative Neurology. 



sition is caudad of the porta and most of the fibres, so far as we 

 can see, are derived trom the caudal cortex, in other words, it 

 resembles the hippocampus commissure and fornix and connects 

 with a descending fornix tract. The early period at which these 

 fibres develop is against their recognition as the callosum. 



In horizontal sections of Menopoma one may trace the 

 fibres from the caudo-median cortex ventrad immediately cau- 

 dad of the porta till a level is reached slightly dorsad of the pre- 

 commissure, here the fibres cross, as described by Osborn. 



These fibres however, can hardly be compared to the callo- 

 sum. Cephalad of the porta and just where one might expect 

 it is a small bundle of fibres which crosses by a strongly curved 

 course from one intraventricular lobe to the other. Study of 

 the embryos of salamanders shows that the tract first above 

 mentiontioned appears early, while the callosum was not found 

 at all. All analogy would lead us to expect that the hippo- 

 campal commissure and fornix would be first to appear and 

 most highly developed in the lower forms. This discovery 

 is in harmony with our view that the cortex is derived from the 

 axial lobes and the commissures with it. (The figures illustrat- 

 ing these statements are prepared but cannot be printed until a 

 succeeding number.) 



The epiphysis in serpents consists of a more or less balloon 

 shaped modification of the original tube and a short stalk which 

 communicates with a spot just caudad of the supracommissure. 

 There are fibres which resemble the connective elements of a 

 parietal nerve arising from the commissure itself but there is no 

 special evidence of nervous function. The terminal bulb itself 

 is contained within a special chamber formed by the adherent 

 meninges and is directed cephalad between the hemispheres. 

 A portion of the pigmented roof above the brain enters the in- 

 tercerebral fissure and is closely associated with the tip of the 

 epiphysis to such an extent that this portion of the organ be- 

 comes invested with chromatophores. No traces of a true par- 

 ietal organ have thus far been noticed. In late embryos of 

 Eutaenia and the black snake the whole region of the dorson of 

 the brain is enveloped in an enormous blood sinus. The epi- 



