Memoir es de la Societe (THist, Nat, de Paris, 53o 



list of distinguished naturalists ; and it is still maintained bj Dr. 

 Leach, on the evidence of the unfortunate Cranch, by Sir EverarA 

 Home, and especially by M.de Biainville. On the other side, names 

 of equally high authority might be advanced. In our own times 

 MM. Bosc, Lamarck, and Cuvier, who in the earlier part of theit 

 zoological career had advocated the doctrine of the parasitic na* 

 ture of the animal in question, have been converted to the oppo- 

 site opinion, and have avowed their belief that the shell and the 

 animal are mutually connected ab 07)0, the former being entirely 

 constructed by the latter. This is also the opinion of M. d6 

 Ferussac, who supports it by several facts observed in a small 

 specimen recently sent to him in spirits, by M. Risso of Nice. 



In this specimen the shell was completely filled by the Cepha- 

 lopode, which was octopodous, and corresponded with the des* 

 cription usually given of the animal found in the JrgonautA 

 jirgo. When thus retracted within the shell four of its arms wer6 

 found to be bent down upon its back within the enlarged keel, lA 

 such a manner, as to apply the suckers with which they ar6 

 furnished, against the internal surface of the keel. The remain* 

 ing four arms were folded, in the opposite direction, into the Spi- 

 ral cavity of the shell, which they filled ; the intermediate pair, 

 or the palmate arms destined to support the eggs, occupyirg thd 

 middle, and forming a mass, over which were folded the extre-» 

 mities of the outer pair, these latter resting, through the greater 

 part of their extent, upon the sides of the body. On breaking 

 the shell, the mantle was found to correspond precisely with its 

 internal surface, presenting a repetition of the sulci, of the broad 

 and flat keel, and of the tubercles which are disposed along its 

 sides. 



This exact accordance of the form of the animal with that of 

 the shell, and its complete adaptation, when retracted, to the 

 different parts of its habitation, are the only facts adduced from 

 observation by the Baron de Ferussac in support of his opinion* 

 His explanation of the probable arrangement and uses of the arms 

 in floating, it is unnecessary to advert to, it being entirely founded 

 on theory. The remainder of his paper consists of arguments drawn 

 from the facts^that no other animal has been at any time found in the 



