532 M. SANDER HANG ON THE ARGONAUT. 



covered it with their large membranes, as we saw when the 

 poulp was swimming in deep water. 



In this new disposition, it will be seen that the difference 

 is great ; for it consists in means and a mode which are no 

 longer the same, and also in the position of the animal, which 

 is such that it finds itself turned over, the ventral surface be- 

 ing uppermost. Thus this mollusc, at once pelagic and lit- 

 toral, presents a most singular anomaly ; when it swims at 

 the surface of the water having its ventral part lowermost, 

 and when it crawls along the bottom having it, on the con- 

 trary, uppermost ; — two things which are completely contrary 

 to what we see among the pelagian molluscs on the one side, 

 and the littoral molluscs on the other. May not this 

 seeming anomaly arise from the circumstance of habit, rather 

 than a profound study, having led us to designate by the 

 name of the ventral part that in which the siphon and the 

 opening of the branchial sac are found, and by that of the 

 dorsal part that which is opposed to it, whilst perhaps it is 

 just the contrary ? However, the learned Professor, whose 

 opinion upon these matters has so much weight with us, re- 

 jects altogether this last idea. 



In this new locomotive power of the mollusc (in which we 

 are of opinion that reptation, as it is generally understood 

 among the Mollusca, was only apparent, the suckers really 

 causing the motion) its progress was slow, and quite differ- 

 ent from what we had previously seen. It worked itself for- 

 wards, like the gasteropodous Mollusca. 



To terminate a description already perhaps too long, but 

 which we judged necessary, in order to give a clear idea of 

 our last observations, we will mention that when the poulp 

 was at the point of death, it drew in, by little and little, its 

 large arms and their membranes, and contracted them upon 

 themselves and all the other arms, so as to obstruct the open- 

 ing of the shell. At this moment we moved the shell, and 

 the poulp immediately separated itself from it, not voluntari- 

 ly but accidentally, for it no longer held it in any way. It 

 appeared at first to reanimate itself a little, made some move- 

 ments in the basin, walking upon its head, then fell from 

 weakness, and very soon died. All this passed in less than 

 ten minutes. We should add that we have repeated these 

 experiments upon many specimens. 



(To be continued.) 



