377 



cases is the same. Contrary to the analogy of other testacea, 

 there is little or no correspondence in the disposition of the color 

 of the Ocythoe and its shell ; the external surface of the skin 

 has the same epidermic covering as in the naked Poulp, and yet 

 the shell has also its delicate epidermis in its natural state ; the 

 shell serves very little for the protection of the body, as its 

 cavity is usually found more or less filled with eggs. Poulps 

 were known to occupy shells parasitically for the deposition of 

 their eggs, even by Aristotle. A naked Octopus has been found 

 imbedded in a wooden pot which had been thrown overboard. 

 Desjardins found a Poulp in the shell of a Dolium ; so that this 

 parasitic propensity is not peculiar to Ocythoe. 



The advocates of non-parasitism — Cuvier, Duvernoy, Ferus- 

 sac,* and D'Orbigny, and others — say that, from the time of 

 Aristotle to the present day, the Argonaut shell has never been 

 found with any other inhabitant than the Ocythoe ; and, what is 

 of greater weight, the Ocythoe has never been found in any 

 other shell than that of the Argonaut — whereas the parasitic 

 Hermit-Crab takes different shells as they fall in his way. The 

 A. argo, nodosa, and Mans, have each a different species of 

 Ocythoe. The shell does not always contain eggs ; Owen alludes 

 to three instances in which it was exclusively and exactly occu- 

 pied by the Cephalopod. 



In addition to the structure and uses of the palmated arms, as 

 already given, it may be mentioned that the nucleus of the shell 

 has not been observed in the egg, it being formed posteriorly, as 

 quoted from Von Siebold ; the structure of the shell indicates 

 secreting organs different from those of other Mollusks, which 

 organs are the palmated arms, as will presently be seen. Young 

 animals have been taken 300 leagues at sea, their shells still 

 cartilaginous, with others adult ; it is hard to believe that they 

 have come this distance in search of a shell, and that they have 

 not formed it themselves. 



Van Benedenf observed two shells, broken in different places, 

 which had been entirely repaired by a matter like the rest of 



* Hist. Nat. des Ct^phalapodes Acetabuliferes, Paris, 1835-48. The most 

 complete account yet published on the Argonaut, and its allied genera — with 

 plates. 



t Nouv. M^moires de I'Acad. Royale de Belgique, Tome XI. 18.38. 



