458 CEPHALOPODA. 



researches of Professor Owen, relative to the analogies that may be 

 traced between the encephalon of these creatures and the brain of 

 higher animals, have served to attach an interest to the study of 

 this part of the economy of the CEPHALOPODA, which has scarcely 

 as yet been sufficiently appreciated by physiologists. 



In the Nautilus Pompilius, the supra-cesophageal ganglion of 

 the GASTEROPODA is represented by a thick round cord of nervous 

 matter (Jig. 212, N), which is in communication with two nervous 

 collars (3, 4) that surround the oesophagus, and likewise with two 

 large ganglia (2) from which the optic nerves take their origin ; 

 but in the Cuttle-fish the same portion of the nervous system 

 (Jig. 215, a) is much more largely developed, and presents a gan- 

 glionic mass of considerable size. If we inquire the reason of 

 this want of correspondence in magnitude presented by the same 

 organ in these two cases, we must necessarily examine the relations 

 in which this part of the brain stands with other circumstances in 

 the economy of the two animals in question ; and we perceive, as 

 Professor Owen has most satisfactorily demonstrated,* that the 

 brain is here developed in accordance wLh the relative complexity 

 of the organ of vision, and also with the perfection of the loco- 

 motive faculties possessed by the Cephalopods under consideration. 

 With the exception of sundry small twigs given off to the mouth 

 and pharynx, the optic nerves (figs. 212, 2; 215, e) are the only 

 ones derived from this part of the encephalon, and, as we shall 

 afterwards see, both the simply constructed eye of the Nautilus 

 and the complicated visual organs of the Sepia are correspondent 

 to the developement of the supra-cesophageal brain ; so that conse- 

 quently the latter may, with every show of reason, be looked upon 

 as the representative of the optic lobes found in the encephalon of 

 fishes,']" and the analogues of the bigeminal bodies in the brains of 

 the higher Vertebrata. 



The ganglia connected with the inferior aspect of the supra- 

 cesophageal mass form two distinct collars embracing the oeso- 

 phagus, an arrangement of which we have already met with an 

 example in Clio borealis among the Pteropod Mollusca. The 

 anterior ring of nervous substance, which no doubt ought rather 

 to be considered as an agglomeration of ganglia than as a simple 



* Descriptive and Illustrated Catalogue of the Physiological series of Comp. Anal, 

 contained in the Museum of the Royal College of Surgeons in London, vol. iii. part i. 

 p. 187. 



f- Cyclopaedia of Anat. and Physiol. ; art. CEPHALOPODA. 



