No. I.] DESMOGNATHUS FUSCA. 245 



sharks, found that he could obtain the same results by separat- 

 ing the olfactory organ from its central connection as by 

 removing the entire forebrain ; from this he concludes that the 

 prosencephal of the shark consists of nothing else but an olfac- 

 tory center, and since the prosencephal of every vertebrate is 

 homologous it further follows that the prosencephal of the 

 vertebrate has developed phylogenetically out of the olfactory 

 organs. A comprehensive definition of the brain is out of the 

 question, but after his numerous experiments and observations 

 he constructs the following formula : The brain is the common 

 center of movement in connection with the function of at least 

 one of the higher sense organs. 



Indeed phylogeny, pointing to the lancelet, lamprey, and 

 elasmobranchs, seems to suggest that the olfactory was the 

 primitive sense as well as segment, and it may be true as sug- 

 gested by Wilder (57) "the prevailing idea that the olfactory 

 lobes are mere appendages of the cerebrum is nearly the 

 reverse of the truth." 



RhincncepJial. — It is a curious fact that the term rhinence- 

 phale as first used by Geoffrey St.-Hilaire and by Robin, had 

 no reference whatsoever to the brain, but was applied to a 

 genus of unocular monsters characterized by the conversion of 

 the nose into a sort of proboscis. Owen applied it to the brain 

 believing that the presence of a cavity in the olfactory bulb 

 entitled it to segmental distinction. Later, Sir William Turner 

 has used the term in a more unsegmental sense. He has pro- 

 posed calling all that portion rhinencephal which is separated 

 from the pallium by the olfactory fissure. Kupffer (24) has 

 made the important discovery that there exists a dorsal neuro- 

 pore in the embryo of Acipenser homologous to the condition 

 found in the lancelet. In the neural tube, as it draws away 

 from the ectoderm at this point, there remains a slight pro- 

 jection which he calls the lobus olfactorius impar constituting 

 the very front of the brain. He has as yet failed to demonstrate 

 its existence in Ammoccetes. Rabl-Riickhard (41) has found a 

 mesal recess in the terma of an Acanthias embryo believed to be 

 homologous with the conditions found by Kupffer. Whether 

 a similar structure can be demonstrated in all vertebrates is 



