156 Journal of Comparative Neurology. 



median and ventral portion of the system passes ventrad to 

 the cephalic part of the lobus infundibuli. Between these 

 are a few bundles of non-medullated fibres of the same char- 

 acter as those which come from the olfactory lobe and cross 

 in the commissure. It may be suggested that the bundle in 

 question is the direct continuation of the tract from the olfac- 

 tory lobe. In the path of both these tracts there are fusiform 

 nerve cells whose processes extend in the direction of the 

 fibres. It is very probable that such cells interrupt some of 

 the fibres. The above system is the chief connection between 

 the prosencephalon and caudal parts of the brain." 



The course of the taenia thalami is the same as usual, 

 though it cannot be traced into the prosencephalon, probably 

 because of its reduced dorsal walls. 



Goronowitsch sums up his views upon the prosencephalon 

 as follows: 



"The cephalic ventrally arched end of the embryonic 

 nerve tube, which, according to Gotte, forms the primitive 

 prosencephalon, is to be regarded as the most primitive phy- 

 letic condition of the prosencephalon which ontogony sug- 

 gests. The primitive prosencephalon is homodynomous with 

 a segment of the spinal cord. By the growth of the dorsal 

 surface of the primitive prosencephalon arose the discrete 

 central organ of smell, while the lobus infundibuli is the 

 result of a protrusion from its base. The formation of the 

 olfactory centre led to the development of the prechordal 

 portion of the skull. The architecture of the cranium of the 

 most primitive of the Gnathostomata, the Notidaidie, corre- 

 sponds to that of the brain. The gradual development of the 

 organ of smell gave rise to the rhinencephalon of recent 

 Selachii. This still indifferent organ exhibits no special 

 homologies with the diencephalon and prosencephalon of 

 higher vertebrates. It is closely connected with the lobus 

 infundibuli, which is reduced in higher vertebrates. 



" On one hand, the reduced form of rhinencephalon of 

 Ganoids and Teleosts is derived from the rhinencephalon of 



