clx Journal of Comparative Neurology. 



Dr. Rabl-Rueckhard follows with a more extended reply to the 

 same article, 1 in which he urges that Studnicka's position is not only- 

 very obscurely stated, but rests upon insufficient evidence, and that, 

 moreover, he has not correctly stated Rabl-Riickhard's views in sev- 

 eral particulars. 



The whole question as to paired or unpaired cerebrum is vain so 

 long as the rhinencephalon is left out of the account. Where the 

 rhinencephalon is paired we may speak of a paired cerebrum. Now 

 the selachian brain^has a very evidently paired rhinencephalon. More- 

 over the development history of this brain shows that in old embryos 

 the cerebrum also originates from paired anlags. Neither are we just- 

 ified in speaking of the teleostean brain as unpaired. Rabl-Riickhard, 

 then, goes further than Studnicka and insists that all vertebrates, not 

 excepting the selachians, possess a paired cerebrum. They can all 

 therefore be reduced to a common type the deviations from which 

 consist wholly in alterations in the walls of the various segments. 

 Thus the selachians differ from the teleosts chiefly in the massiveness 

 of the roof of the cerebrum. Now, conceive the internal dualism of 

 the teleostean brain to become evident externally by the appearance 

 in a massive dorsal wall of the falx cerebri primitiva and we have 

 practically the amphibian brain. Not only is it possible to derive the 

 selachian brain directly from that of the amphibians, but the fissura 

 hippocampi (Edinger) is already indicated in the prosencephala roof 

 of selachians. 



In the : fish brain Studnicka would make the pallium a tela. This, 

 our author insists, would relegate it to the diencephalic roof; but this 

 is impossible because it is on the wrong side of the velum. Rabl- 

 Riickhard does not here consider the possibility of homologizing the 

 pallium with the paraphysis, nor does Studnicka himself mention it 

 in this paper, though he does so in a later communication. 



The conclusion is drawn that the Cerebrum of all Craniota with- 

 out exception is in its most cephalic portion always paired ; but that 

 this fact is no way weakens the author's views of the structure of the 

 teleostean brain. He declines to attempt the construction of a phylo- 

 genetic tree, but gives instead a page of drawings of sagittal sections 

 of the hemicerebrum entitled "Schema der phylogenetischen Entwick- 

 elung des Vorderhirns." In this plate the types figured are arranged 



^as'^Vorderhirn der Cranioten. Eine Antwort an HerrnlF. K. Studnicka. 

 Anat. Anz., IX, 17, June, 1894. 



