12 Mr. A. Hancock on the Nervous System 



also in general character moUuscan. Tlie Cephalopods, however 

 aberrant in external appearance, would therefore seem to be true 

 mollusks. 



On taking a glance at the vascular system, the same conclu- 

 sion is inevitable. Milne-Edwards states, in his article on the 

 circulation of the " Poulpe,'^ that the arterial system of the Ce- 

 phalopods is fundamentally the same as in the Gasteropodous 

 and Acephalous mollusks ; and the heart itself, though consider- 

 ably modified, he assimilates to that of the Acephala. It is truly 

 systemic, having superadded, to meet the changed and active 

 habits of these creatures, additional propelling organs appended 

 to the gills*. In Nautilus these latter are deficient, the central 

 apparatus being reduced to a true molluscan ventricle. There 

 is no true pericardium, and the great chamber in which the 

 blood- propelling organs are placed appears to represent the 

 renal cavity in Doris ; but whether truly so or not, it is probably 

 of the same functional purport. The glandular nature of the 

 walls of the great venous trunks congregated in that chamber 

 cannot fail to suggest the idea that it is designed for the recep- 

 tion of some copious outpouring from the blood ; and as it 

 opens externally by two minute orifices at the roots of the 

 gills, its similarity to the renal organ in Doris is almost com- 

 plete. The portal heart, which in that mollusk is connected 

 with this organ, is indeed at present not determined, though 

 it is very likely that the two " fleshy organs " appended to the 

 branchial hearts will prove to be ventricles for propelling venous 

 blood into the liver. These fleshy organs in Ommastrephes 

 were examined and found to be hollow, muscular and heart-like, 

 communicating through their pedicle with the branchial hearts, 

 and having the orifice guarded by a valvular constriction. The 

 free side is perforated in the centre, the lips of the orifice being 

 jagged as if torn from a vascular attachment. There can be 

 little doubt that these are organs for propelling blood, and that 

 too in a venous state, and to determine this fact, all that is 

 wanting is a favourable opportunity; but it unfortunately happens 

 that the region of the heart is most liable to laceration ; the spe- 

 cimens examined in this instance were ruptured in that locality 

 by rough handling when captured. 



Thus we see that the vascular system of the Cephalopods is 

 likewise formed on the molluscan type, and the digestive system 



* These are not the only additional blood-propelling organs in Omma- 

 strephes. The posterior aorta previous to sinking into the fin is (hvided 

 into two branches, which, as they penetrate the fleshy substance, are each 

 dilated into a small but well-defined ventricle ; these ventricles will un- 

 doubtedly throw the blood with increased force into this powerful muscular 

 organ. 



