402 The Inhabitant of the Argonaut. 



intended to hold, so as to retain, in the first-mentioned, a more 

 or less spiral shell; in the latter, the valve of a bivalve, or an 

 alcyonite, or a spunge ; that is to say, it is a simple relation of 

 cause and effect, by means of a preestablished harmony. The 

 great membraniform expansion of the arms of the Ocythoe 

 was a provision necessary to secure the power of prehension, 

 the holding firmly a patulate or open-mouthed shell, which, 

 without that, would be liable to fall by the slightest move- 

 ments, and that by a soft animal, not at all resembling in its 

 state that which exists, for example, in the Cyprae v ae. In 

 these latter, indeed, it is not the lateral lobes of the body 

 which produce the shell, but they merely modify it, by thick- 

 ening it, in a gradual manner, more or less irregularly, and 

 by leaving in the medio-dorsal line an indication of the more 

 or less immediate approach of the two lobes. We see ab- 

 solutely nothing similar to it in the shell of the Argonaut, 

 which is always extremely thin, every where of equal thick- 

 ness, with very finely marked lines of growth, without any 

 deposit of shelly matter, unless it be upon the auricles at the 

 extremity of the columella ; nor is its form, either generally 

 or in part, explained, in any probable manner, by the Octopod 

 which inhabits it. 



As to the argument drawn, by M. Rang, from the deeper 

 colouring of the base of the palmated arms of the Ocythoe, 

 showing itself, also, upon the corresponding part of the shell, 

 we may easily look upon it as only an imbibed colour, without 

 exceeding the bounds of analogy, since all the Nautilus shells 

 do not exhibit this colour. But this argument is much too 

 slight (the colour not being even similar) for us to be able to 

 find in it an argument of any weight in a question so im- 

 portant, scientifically speaking. 



Notwithstanding that we put a construction so different 

 from M. Rang, as to the use of the observations which he has 

 communicated to the Academy, in the solution of the problem 

 respecting the parasitic nature of the Cephalopods with pal- 

 mated arms, we do not the less appreciate his very interest- 

 ing communication; at the same time that we would request 

 him to continue employing in the service of natural history 

 the leisure which the duties of his station may allow him. 



We shall take the liberty of proposing to him the follow- 

 ing observations, if he should again be placed in a position 

 favourable for elucidating the point of natural history in 

 question : — 



1st, To make the animal quit its shell, as Cranch has done, 

 and note that which results from it. 



2dly, To make this experiment not only on dry land, but 



