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 naturalists 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 Ocythoé Cranchii, that ‘‘ all the internal or- 
gams 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 pancreatic bag is of a triangular form, and not spirally disposed ; the two simple 
biliary 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 branchie, 
and they terminate at a greater relative distance from the base of the funnel. 
1 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 observations 
of M. Rang, Comptes Rendus del Acad. des Sciences, Ayril 24, 1837. 
