186 



THE NAUTILUS. 



pretend to vouch; we only allude to them, because they go to 

 prove, that some enormous Cephalopoda is frequently met 

 with, which credulous navigators have readily transformed 

 into this extraordinary monster.* 



Did you not say, mamma, that the Paper Nautilus (Jlrgo- 

 nauta argo) belongs to the family of Cephalopoda? 



MRS. F. 



I did say so. I suppose you have all seen pictures of this 

 animal st&mminff on, the surface of the water, erecting its two 

 largest re*'aculai&j^arms) for sails, employing the other six 

 as oars, and its shell as a boat? Nothing, I should think, 

 can present a prettier sight. In fine weather they are to be 

 seen in troops in the Mediterranean, but descend immediately 

 on the approach of rough weather, or of danger. In order to 

 effect this, the Nautilus draws in water to add to its weight, 

 and thus is enabled to sink into the depths of the ocean. 

 When it wants to re-ascend, it diminishes the specific gravity 

 of its shell by ejecting the water, and thus again rises to the 

 surface of the sea. The Jlrgonauta argo does- not appear to 

 adhere to its shell, whence many naturalists have imagined 

 that the animal which inhabits it, is parasitic, occupying, 

 like the hermit crab (Cancer Bernhardus^the shell of another. 

 But, as this animal is always found in this shell, and no 

 other has ever been seen to inhabit it, although the shell is 

 common, and often seen on the surface of the sea, we have 

 every reason to deem this opinion to be highly problematic. 



MARY . 



Pray, mamma, what is that enormous shell which Mrs. 

 Clifford has in her hot-house to hold some of the smaller 

 kinds of water plants? 



MRS. F. 

 It is the Chama gigas, a shell which sometimes attains an 



* Dictionnaire des Sciences Naturelles, &c. 



