10 M. SANDER RANG 



known, does not adhere to its shell by a muscle, or even a 

 collar, it is therefore very necessary that it should have some 

 organ to hold it by ; and, if we do not deceive ourselves, 

 there lay perhaps one of the difficulties which most clogged 

 this naturalist in developing his whole ideas upon the para- 

 sitism of the mollusc in question, for it was impossible, with 

 the knowledge which he has of the organization of this ani- 

 mal, that he should believe, like some naturalists, that the 

 poulp made use of its suckers as a means by which to adhere 

 to its shell. M. de Blainville sees then, in this abnormal or- 

 ganization of the large arms of the poulp, an arrangement 

 necessary for its maintaining its position in the shell that it 

 inhabits, and, without which, it would be every moment ex- 

 posed to the loss of it. This is a fact incontestably demon- 

 strated, and which cannot fail to be adopted indifferently by 

 the partisans of non-parasitism, and those of parasitism. 



Should it be objected, (for it is necessary as much as possible 

 to anticipate objections), that the poulp can have no need to 

 cling so strongly to its shell, because the effort that it makes 

 to expel the w ater from its branchial cavity, when swimming, 

 far from tending to separate the two, only on the contrary 

 brings them closer together ; — it would be easy for us to re- 

 ply, that the movement does not consist merely of remo^^al : 

 and, that without speaking of shocks, of the agitation of the 

 waves, &c., it is very natural to suppose that when the mol- 

 lusc crawls along, carrying its shell with the opening turned 

 downwards, the shell could not fail to escape, and mount to 

 the surface of the water, on account of the air which it indu- 

 bitably contains, if the poulp did not retain it by some means 

 as constant and as powerful as those which it possesses. 



The position of the large arms with their membranes over 

 the shell, and the service which they render to the poulp, 

 being once made known and adopted, let us see what are the 

 inferences which may yet be drawn from this fact to throw 

 light upon the question, and simplify it from the chaos of ar- 

 guments presented on all sides, and generally derived from 

 facts wrongly interpreted, or from pure imagination. 



Those naturalists who have turned their attention to the 

 argonaut, have been very little agreed as to the relative posi- 

 tion of the poulp to its shell ; and from this there has re- 

 sulted — first, the inconvenience of not being able sooner to 

 explain the use of the membraniferous arms; — and, secondly, 

 a supply of weapons to the partisans of parasitism ; for these 

 latter have skilfully seized uj)on this disagreement to draw 

 from it this certainly rather rational argument, that, since the 

 mollusc adheres sometimes in one manner, and sometimes in 



