500 Mr. Garner on the Nervous System of Molluscous Anhnals. 



The nervous system of the Cephalopoda, then, has some resemblance to that 

 of a fish. In one circumstance it differs from those of all vertebrate animals, 

 viz. the brain has not yet entirely ascended over the oesophagus, but forms a 

 ring around it. Without any stretch of fancy, the superior lobe may be com- 

 pared to the optic lobes of a fish, or the corpora quadrigemina ; and the an- 

 terior unlobed part of this ganglion is, perhaps, a rudiment of the hemispheres. 

 But hence olfactory nerves ought to arise, as optic nerves do from the optic 

 lobes, and form olfactory nerves. The nerves going hence form in fact a 

 ganglion, which the author has called labial, but which gives a great number 

 of nerves to two membranous parts around the maxillse, the external one of 

 which appears analogous to a membrane, which, in the Nautilus, Mr. Owen 

 tells us, is of a structure identical with the olfactory laminae of fishes, and to 

 which he actually gives the name of olfactory organ. There is no rudiment 

 of a cerebellum, which organ is, however, sometimes in a rudimentary state 

 in reptiles. As we see in fishes large lobes developed on the olfactory nerves, 

 we here see them on the optic. The eyes are as highly developed as those of 

 many vertebrated animals, and hence the size of these lobes : to what parts 

 of fishes, however, are they, and the little geniculata upon them, analogous ? 

 The pharyngeal ganglion and nerves supplying the jaws, tongue, maxillae, 

 salivary glands, muscles of deglutition, and forming the principal attachment 

 or origin superiorly to the sympathetic, must be analogous to the ganglionic 

 fifth nerve of higher animals. Its nerves of connexion are probably from two 

 sources, two of those going from the anterior part of the superior lobe belong- 

 ing to it, as well as the band of motor nerves from the pedal ganglion, going 

 to it through the labial or olfactory ganglion ; the fifth nerves here, as in 

 other animals, being connected with the olfactory. The lower part of the 

 cerebral circle evidently (with the exception of the pedal ganglion) gives off 

 the same nerves as the medulla oblongata does in higher animals, — the exter- 

 nal respiratory, acoustic, and branchio-visceral nerves. It receives from below 

 two large columns, the position of which is similar to that of a spiral chord. 

 External to these large nerves or columns is a large ganglion, which is con- 

 nected to it by two separate bands : this ganglion gives its branches to the 

 mantle, whilst the rest of the branches given by the nerve are distributed to 

 the fin ; all these nerves passing to their destination between cartilages, per- 



