IN VEETEBEATES AND INVEETEBRATES. 11 



the topical relations of these parts to the gullet are the same in 

 both great divisions of Invertebrates, and that the homologies of 

 the aforesaid parts vrith the primary divisions of the Vertebrate 

 brain are affected solely by the altered relation thereto of the 

 gullet and mouth. 



The homologies of the Dibranchiate brain, notw^ithstanding the 

 oesophageal and oral differences and a non-appreciation of their 

 essential nature and cause, were recognized and affirmed by the 

 Father of the anatomy of the MoUusca. They are clearly ex- 

 pressed in the first of his immortal ' Memoires '* on that subject ; 

 and are briefly summarized in the ' Legons d' Anatomic comparee.' 

 After describing the " sub-" and " supraoesophageal " centres, 

 Cuvier afiirms : — " On pourrait comparer le premier au cervelet, 

 I'autre au cerveau des Vertebres." If for " cerebellum " one 

 writes " epencephalon," this defined correspondence of the brain 

 of the highest Mollusks with that of the lowest Vertebrates would 

 square with my own convictions. 



But now I am driven to ask, Why did Cuvier refuse to extend 

 his views, whether homological or analogical, of the answerable 

 parts of the brani in Vertebrates and Invertebrates beyond the 

 " supraoesophageal" mass or ganglion in Mollusks and Articu- 

 lates ? Because he declined to extend those views in relation to 

 the Vertebrate and Invertebrate encephalic centres beyond or 

 below the higher order of Cephalopoda; and he logically pro- 

 nounced, at the conclusion of his admirable anatomical mono- 

 graph of the "Poulpe" {Octopus vulgaris), that the class of 

 which it was the type — my Cephalopoda Dibranchiata — formed 

 not the passage to any other group, and that they have not re- 

 sulted from the development of other animals, and that their own 

 development has produced nothing superior to themf. It must 

 be remembered, however, that the transitional modifications of the 

 Tetrabranchiate Cephalopods had not at that date been made 

 known. 



If, however, the cerebral homologies may be traced, with the 

 guidance of the Pearly Nautilus, through the still lower, more 

 simplified Mollusca, notwithstanding their retaining more of the 

 lower and primitive circumoral type, my next contention is that 



* ' Memoires pour servir a I'llistoire et I'Anatomie des MoUusques,' 4to, 

 1816, Mem. P"", " Sur le Poulpe ( Octopus vulgaris)." 

 t ' Memoire sur le Poulpe,' op. cit. p. 43. 



