530 M SANDER RANG 



and their membranes, and this is perhaps what they wished 

 to represent ; but even then we shall show that they are in 

 error, for when the poulp makes this movement, which ap- 

 pears to be a voluntary one, it draws in its arms backwards, 

 and uncovers the shell only in front, so that the anterior edge 

 of the membrane retires parallel to itself, as well as to the 

 furrows of the shell. As to the reversion of a portion of the 

 membrane which is represented, — we have never observed it, 

 and we must remark with respect to it, that this membrane, 

 which, in the living animal, appears as we have already said 

 closely applied to every part of the shell, merely glides over 

 it when it retires or advances, exactly as do the lobes of the 

 mantle of the cowries and olives, or merely the appendages 

 of the latter. We must further observe that we have never 

 seen the eggs in the place where they are represented in the 

 plate in question, but much more within the opening. 



To return to the description of our poulp, which we left 

 contracted within the argonaut- shell, and watching, with an 

 attentive eye, whatever took place around it; we now see it 

 extending itself from out its shell, and protruding six of its 

 arms, then it throws itself into violent motion, and travels 

 over the basin in all directions, often dashing itself against 

 the sides. It is easy for us to observe that in these different 

 movements the body leans a little towards the anterior part 

 of the shell ; and that the long slender arms, very much ex- 

 tended and gathered into a close bundle, are carried before it, 

 as well as the tube, which shows itself open and very much 

 protruded. The large arms are extended along the keel, and 

 their membranes carpet the whole of the shell. As to loco- 

 motion, it is effected in the ordinary manner of poulps, that 

 is to say, it progresses backwards by means of the contraction 

 of the sac, and the expulsion of water through the siphon. — 

 We have endeavoured in our second plate 1 to represent the 

 disposition of the mollusc of the argonaut under these cir- 

 cumstances ; and it appears to us easy to see that all is there 

 contrived in a manner the most favorable for accelerating the 

 progression of the animal. In fact the lightness of the shell, 

 its narrow and keeled form, its width, least at the part which, 

 presenting itself first, has to cleave the ambient element; — 

 that membrane, which on each side carpets the shell, like a 

 sheath intended to make its inequalities disappear, and to fa- 

 cilitate the gliding of the water ; — this bundle of arms extend- 

 ed behind the animal, to oppose the least possible resistance; 

 and then, lastly, the two arms stretched like a bridge over the 



1 Plate 5 of the Supplementary Illustrations. — Ed. 



