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 Ocythoé of reproducing, or otherwise, the Argonaut shell, 
would be an ezxperimentum 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 hians 
of Solander, and the animal is the Ocythoé 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 hiuns 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 Ocythoé, that the Argonaut shells taken 
possession of by different species of Ocythoé 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 rufa. 
2 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 Ocythoé 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 expelled by the Ocythoé, 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 the 
* Annales d' Anatomie et de Physiologie, Mai, 1837. 
