SOME NEW AND RARE CEPHALOPODA. 117 



and in Arg. Argo they are visible to the naked eye, and extend round the whole of the 

 circumference of the same part. From this disposition of the suckers it would appear as 

 if the characteristic structure of the first pair of arms arose from their extremities being- 

 bent back upon themselves and united to the stem by means of a thin membrane. These 

 membranes are most developed in the Mediterranean species, the Argonauta Argo, and 

 have been described by naturahsts and poets from Aristotle and Callimachus down to 

 Cuvier and Byron, as serving the office of sails ; the animal being supposed to have the 

 power of rigidly extending the soft fleshy arms which support the membranes, and of 

 maintaining the latter tensely outstretched to meet the breeze. It is scarcely necessary 

 to observe, that the structure of the parts in question is incompatible with this hypo- 

 thesis of the use of the vela in navigating the frail boat of the Argonaut'. 



In the present species the terminal membranes of the first pair of arms are relatively 

 smaller than in Arg. Argo or in Arg. tuberculata : in the latter they are broader than 

 they are long : in the Argonauta hians they present contrary proportions. In the present 

 specimen in which the vela are beautifully entire, they measure from the commencement 

 of the reflected portion of the arm, (or what would be considered as the end of the arm) 

 to the lower margin of the web, four lines, their breadth is three lines. The length of 

 the second pair of arms is ten lines, the number of suckers, fifty-six ; the length of the 

 third pair eight lines, number of suckers fifty-two ; the length of the fourth pair seven 

 lines, the number of suckers twenty-eight. 



Dr. Leach observes, in his description of Ocythoe Cranchii, that " all the internal or- 

 gans are essentially the same as in the Polypus." [Octopus of Cuvier, loc. cit., p. 294.) 

 We found, however, that the Argonauta hians, like the Argonauta Argo, receded from 

 the naked Octopods, Octopus and Eledone, and approached the Decapods in the struc- 

 ture of the branchial hearts, which are provided with a fleshy appendage ; and in the 

 form of the appendages to the vena cava which are shorter and thicker ; and in the re- 

 lative position of the lozenge-shaped ink-bag, which is not buried in the substance of 

 the liver, but lies in its anterior concavity. The inferior salivary glands are also rela- 

 tively smaller. 



The following differences, as compared with the Octopus, occur in other internal or- 

 gans which adhere to the type of structure which characterizes the Octopodous tribe of 

 Dibranchiata. The crop increases in width as it approaches the stomach. The lami- 

 nated panci-eatic bag is of a triangular form, and not spirally disposed ; the two simple 

 biUary ducts enter at its apex. The two oviducts are devoid of the circular laminated 

 glands which surround them about the middle of their course in the Octopus ; they are 

 also disposed in four or five convolutions as they pass behind the roots of the branchice, 

 and they terminate at a greater relative distance from the base of the funnel. 



' Since the above was written, it has been, ascertained by direct observation, that these vela, or rather vela- 

 menta, have not only a relation of coexistence, but one of direct physiological import, to the development of the 

 shell in the Argonauts, serving as the organs both of secreting and of retaining this part. See the obsen'ations 

 of M. Rang, Comptes Rendus de V Acad, des Sciences, Avril 24, 1837. 



