114 MR. OWEN'S DESCRIPTIONS OF 



the power of either producing or reproducing the shell, must be sufficient to decide that 

 the one usually found in it, is not the original inhabitant of the shell." 



With respect to the remark with which my friend concludes his observations on the 

 present specimens, I need scarcely observe that there is no doubt that the determination 

 of the power possessed by the Ocythoe of reproducing , or otherwise, the Argonaut shell, 

 would be an experimentum crucis, and settle the long-agitated question. I do not find, 

 however, among the notes left by Mr. Bennett in my charge, any other observations re- 

 specting the Argonaut than those above transcribed ; and the experiments hitherto re- 

 corded touching the reproduction of the shell by the Cephalopod inhabiting it, have been 

 deemed by the experimenters as proving that the shell is the veritable production of the 

 Cephalopod. 



The shell of the specimen under consideration belongs to the species Argonauta Mans 

 of Solander, and the animal is the Ocythoe Cranchii of Dr. Leach, so called on the sup- 

 position of its being a parasitic inhabitant. It is worthy of remark, that in the present, 

 as in every other instance of which I have cognizance, where the Argonauta Mans has 

 been taken with its inhabitant, the latter has invariably presented characters as speci- 

 fically distinct from those of the Cephalopods inhabiting the Argonauta Argo and Argo- 

 nauta tuberculata as are those of the latter from each other : and the same circumstance 

 holds good with respect to a nondescript species of Argonaut\ taken by Capt. P. P. King 

 in the South Pacific ocean ; in which both the shell and its inhabitant differ specifically 

 from the three recent species hitherto described. I am aware that it has been urged by 

 the advocates of the parasitic nature of the Ocythoe, that the Argonaut shells taken 

 possession of by different species of Ocythoe in different parts of the ocean would be most 

 likely to be also of distinct species : but the constancy of the correspondence between the 

 Cephalopod and the shell, both as to specific peculiarities and size, affords strong pre- 

 sumptive evidence of their relation to each other being something more than mere acci- 

 dental adaptation". 



• This species I have called, from the colour of the animal and its shell, Argonauta riifa, 

 ^ Since the preceding observations were written, the following facts have been added to the natural history 

 of the Argonaut. M. D'Orbigny states that he has observed specimens of the Ocythoii in Argonaut shells, of 

 which the margin of the aperture was entire, and in a membranous or soft state ; whence he concludes that the 

 shell had recently received an addition at that part, and that this addition was due to the Cephalopod inhabiting 

 it. It is difficult to assent to the explanation of this fact offered by M. De Blainville*, viz. that the true con- 

 structor had been very recently e.xpelled by the Ocythoe, for in that case the very delicate margins of the shell 

 would surely have been injured by the Cephalopod whilst violently expelling the rightful owner, and usurping 

 possession of the fragile shell. 



Two experimenters (Madame Power and M. Rang), at different periods, and in different places, have broken 

 and removed portions of the Argonaut shell while inhabited by the living Cephalopod, and have observed that 

 the latter repaired the breaches by a secreted substance, not indeed similar to the originally formed shell, but 

 which one of the experimenters, M. Rang, compares in this respect with the shelly matter secreted by tlie 



* Annales d' Anatomic et de Physiologic, Mai, 1837. 



