MAUINE ANIMALS. 275 



cavities, and which is not wholly displaced by the water taken in; for this 

 purpose, those portions of the tube which pass through the cavities are 

 furnished with a very beautiful apparatus representing valves, so contrived 

 as at once to expel or drink in water; and therefore the commonly received 

 notion of the animal filling its shell with water to sink, is the correct one, 

 although, as a broad unexplained assertion, it gives but a very imperfect idea 

 of the true operation. 



As I have before observed, in casually referring to this class of Marine 

 Animals, the poetical notion of the sailing propensities and capabilities of 

 these beautiful creatures is altogether without foundation. It may seem 

 an ungracious task to dispel that which has furnished the poet with so many 

 themes of song, or the painter with so many materials for his pencil; but 

 as a faithful delineator of nature, I am bound to dispel this fable, and put 

 the matter upon its real footing. Thus, what are called the sails, are nothing 

 but a part of the mantle or interior membrane, which covers all this class 

 of animals, and extended in this instance to protect the sides of the shell, 

 around which, when on the surface of the sea, they are usually wrapped. 

 Doubtless the arms or tentacula assist the shell in its movements on the 

 water, but it much more often floats than is propelled; arid the ordinary form 

 in which it appears, is with some two or three of the arms hanging over the 

 sides into the water, and the others protruded forward after the manner of the 

 horns of a snail, the velamen, or protruding mantle, either loose, or wrapped 

 around the shell; and when at the bottom of the ocean, they crawl with 

 what would be called the shell upside down; that is, in the very reverse 

 position to that in which they appear on the surface. 



Those layers of shell which divide the cavities I have above referred to, 

 are secreted one by one behind the animal as it grows larger, and thus the 

 number of cavities would of course enable us to determine its age, having 

 once ascertained how long one of these cavities is in forming; but of this 

 I shall not speak at present; suffice it now to say that the animal resides only 

 in the outermost portion of the shell, the whole of the cavities being filled 

 with air only, and the agents whereby it sails or swims. The general for- 

 mation of tho body greatly resembles that of the starfish, but this likewise 

 I shall for the present defer minutely describing; merely adding that any 

 doubts, which might formerly have existed, with reference to the fact of the 

 animal being the owner and former, as well as the inhabitant, of the shell, have^ 

 been long since set at rest by numbers of Argonauts being kept in a state 

 6f captivity alive, and the shells being in numerous instances fractured and 

 repaired by the creatures themselves. In my next paper on this elegant 

 class, I shall refer particularly to the different genera. 



(To be continued.) 



