clviii Journal of Comparative Neurology. 



by median section recur in the brain of the Sauropsida with certain 

 modifications. Since these modifications consist chiefly in displace- 

 ments of the vertical [dorsal] plate between the post-commissure and 

 the recessus neuroporicus, and since the shortening of this region is 

 accompanied by the elongation of the lamina terminalis, I think that 

 I may be justified in concluding that these modifications may occur 

 under the influence of the highly developed cerebrum, especially its 

 hinder part, in the Sauropsida. The structural plan of the median 

 section is in other respects the same as in the Ichthyopsida. The 

 ependymous portions of the brain, which appear most constantly in 

 median section, have the highest significance as primitive structures. 

 They will attain for the comparative anatomy of the nervous system 

 the same importance as cartilage for the comparative anatomy of the 

 skull." 



In a third communication 1 he attacks the fore-brain of fishes, that 

 " most variable part of the fish brain." The difficulty experienced 

 by observers hitherto has been to refer the diverse forms of fish brains 

 to a type which may serve as a criterion. Such a type this author 

 finds in Notidanus. Not only are all transitions in cerebral structure 

 from the teleosts back to the ganoids present ; but the cerebrum of 

 ganoids also possesses the closest resemblance to that of the Notida- 

 nidae, the Holocephali, and to Ceratodus as the most primitive of the 

 Dipnoi. The criteria of judgement for the cerebrum of fishes center 

 about the morphological properties of the lamina supraneuroporica 

 (Kupffer's " praepinealis Zwischenhirn" and " Palluim des Parenceph- 

 alon "), its limits and relations to the walls of the cerebrum, together 

 with the characteristics of the adjacent cerebral walls and the extent 

 to which they are thickened. The attempt is made to derive the sela- 

 chian brain from that of Notidanus, but the author adds that the 

 peculiar structures by which the mass of the cerebrum is increased in 

 selachians are so totally different from those employed by higher ani- 

 mals that we may question whether their hemispheres may be com- 

 pared with those of higher animals. Finally the conclusion is drawn 

 that, using as morphological data the extent and properties of the 

 lamina supraneuroporica, the thickening of the prosencephalic walls, 

 the relations of the ventricles and olfactory lobes, it is quite possible 

 to refer all these different forms to a common type. This type is char- 

 acterized by having the whole cerebrum, whose walls are of uniform 



J Zur vergleichenden Anatomie des Vorderhirns bei Fischen. Anat. Anz. 

 IX, 12, April, 1894. 



