1882.] Prosencephalon of Teleosts. 119 



reptilian brains; and, third, to the discovery made by my 

 pupil, Mr. Turner, that in the brain of birds there are several 

 introverted cortical niduli within the axial lobe, in regions 

 where the cortex is restricted or aborted. 



In general, then, it seems proper to regard the cerebrum as a 

 product of a dorso-lateral pouch from the thalamus, carrying 

 with it the commissural systems (dorsal and ventral) belonging 

 to what may be called the prsethalamic segment or neuromere. 

 The hippocampal system may be regarded as representing a 

 'part of the dorsal commissure, the callosum a pan of the ven- 

 tral and perhaps part of the dorsal, while the anterior com- 

 missure is decidedly ventral. 



At any rate the morphological relations in fishes are precisely 

 as in higher vertebrates. The conclusions above indicated may 

 be thus summarized. 



1. Fishes have a < 

 and on the opposite 

 missura. 



2. Fishes have a distinct fornix and hippocampal coin- 

 normal fibre connections. 



4. There are distinct radices mesalis and lateralis in the 

 ichthic olfactory lobe, the former crossing in the anterior 

 commissure, the latter passing to a hippocampal lobe. 



5. The hippocampus of fishes is a distinct lobe of the axial 

 part of the cerebrum. 



6. The axial lobe in fishes is composed not only of the 

 elements proper to the corpus striatum or sauropsidian axial 

 lobe but also contains rudiments of the sensory and motor 

 niduli of the cortex. 



7. The two types of cell- are sharply differentiated. 



Horizontal longitudinal sections through the i 

 ie drum, Haplodinotus grunniens. 



