HANCOCK OX THE ANATOMY OF DIBBAM 11 1 ATI: CEPHALOPODA. 483 



wall of the former : but here, as in the other group, there is no 

 pericardial sac. 



The heart itself is strong and muscular, and fche fibres are of the 

 striated kind. Those of the branchial hearts are also apparently 

 striated, but the stria* are less distinct, owing perhaps to the state of 

 preservation of the specimen examined Striated fibre has likewise 

 been observed in these parts by H. Midler. 



The ascending aorta, on reaching the cranium, is divided into two 

 nearly equal portions, each of which has, near its origin, a conspicuous 

 bulbous enlargement. Numerous branches radiate from these bulbs, 

 and are distributed to the brain, to the eyes, to the oesophagus, to the 

 salivary glands, to the buccal organ, and to the arms. The branches 

 that goto the buccal organ pass through the nervous collar ; and that 

 which supplies the arms goes so far along with them, and then pene- 

 trating through the pedal ganglion, passes to its outer surface, and so 

 advances to its destination, giving off, as it goes, branches to the mus- 

 cular wall of the buccal channel. 



The arterial branches supplying the fins in the Loliginidce, exhibit 

 enlargements similar to those of the aortic branches, and the function 

 in both cases is probably the same, though it is not very clear what 

 it is. As they are muscular, however, they are probably for the 

 purpose of regulating the flow of the blood to the respective parts, 

 retarding it or pressing it onward, as occasion may require. 



The most interesting point that I have observed in the nervous 

 system is, that the surface of the brain of Octopus vulgaris displays 

 distinct inequalities, having a considerable resemblance to the rudi- 

 mentary cerebral convolutions of some of the lower Vertebrata. I 

 have also, for the second time, observed that the brachial nerves 

 originate in two centres, or rather, that in those species which have 

 the pedal ganglions divided into two portions, these nerves have 

 double roots which can readily be separated for a considerable dis- 

 tance from their origin. 



It may also be stated, that, on a due analysis of the parts, the 

 connnissures and the ganglions, composing the Cephalopodous brain, 

 can be clearly determined, and their homological relations with those 

 of the lower mollusks ascertained. This being so, the difficulties 

 with regard to the general homologies of these highly organised 

 mollusks do in a great measure disappear. And it is satisfactory to 

 know, that the results, thus obtained, agree with those derived from 

 embryological and other data, as determined by Prof. Huxley. 



In concluding these few somewhat hasty and imperfect remarks, 

 on the structure and physiology of the Dibranchiate Cephalopoda, 

 it will be well to take a glance at the results at which we have 

 arrived, though in some respects they cannot be considered final. 



The results, then, are as follows : — 



First. — That the so-called abdominal or visceral chamber, in the 

 Dibranchiate Cephalopoda, is a veritable venous sinus, formed by the 

 expansion of venous trunks, and that it is provided with proper walls. 



