378 



the shell. De Blainville believes the Poulp of the Argonaut 

 shell is a parasite ; the exceptional expansion of one pair of the 

 arms, he thinks, is for maintaining the animal in the shell by- 

 embracing its exterior, as the hooks of the Paguri, among Crus- 

 taceans, serve to fix the latter animals in their borrowed shells ; 

 while M. Rang sees in this arrangement a new argument in 

 favor of non-parasitisra. The parts found repaired were the 

 middle of the sides, the lower free border, and near the back. 

 In the first, the reproduced part had not the transverse ribs nor 

 tlie striae of increase ; it was more convex than the shell, with a 

 corresponding internal depression ; it was produced beyond the 

 broken surface, especially on the inside ; laminated like plates of 

 mica. By chemical reaction, the new was shown to be like the old 

 shell ; there being, however, less carbonate of lime according to 

 the superficiality of the layer, the external having very little, and 

 apparently serving for an epidermis — the part broken being 

 thus reproduced like the formation of the entire shell, which at 

 first is membranous.* In the reparation of the free edge there is 

 the same polish as on the rest of this edge, as if it were covered 

 with a layer of enamel. If the palmated arms can thus produce 

 a polished surface on the border, as the Cypraea does over its 

 whole shell by means of its mantle, it is a strong argument in 

 favor of non-parasitism ; for the supposed constructor of the shell 

 allied to Carinaria, could in no way polish this surface. Is it 

 probable, then, that an animal having no shell, should have an 

 apparatus capable of secreting, in case of need, matter proper 

 for repairing with similar tissue a shell not its own, and also of 

 depositing a layer of enamel on the free border at the place 

 where its palmated arms come out in order to embrace the shell? 

 It can hardly be doubted that this Poulp is not only the inhabi- 

 tant^ but the maker of its shell. 



It is very curious that among the great number of Argonauts 

 examined by different naturalists, not a single male has been 



* Dr. Warren has also a fine specimen of A. nodosa, in which a fracture of 

 one side of the shell had been completely and beautifully repaired; and a 

 specimen was exhibited showing the partial closing of a fracture by a thin 

 membrane. This reparation, according to Madame Power, takes place with 

 great rapidity; she has seen a large opening covered over by membrane in less 

 than six hours. 



