RELATION OF SHELL AND ANIMAL. 401 



tion the hypothesis rather from respect to its able advocates 

 than from any the slightest conviction of its truth. It is 

 inconsistent with analogy to believe that the Mollusca are 

 influenced by the sexual passion long previous to the attain- 

 ment of maturity ; yet the hypothesis assumes that some 

 of them feel its power almost from the date of their birth, 

 and afterwards at very short and frequent intervals ; while 

 others, of the same genus even, are swayed by it at distant 

 periods, and only two or three times during the term of 

 their existence. And in what predicament are those which 

 are plain and ribless ? Are we to believe that their life is love 

 unceasing ; or that it begins only when the animal reaches 

 maturity, and is about to finish the aperture of its edifice ? 



In the progress of its formation, the shell of every class 

 is moulded on the mantle of the animal, and when placed in 

 your cabinet you have in the shell a permanent cast of the 

 form and the main peculiarities of the latter. Every line and 

 plait of the mantle is most accurately imprinted on the inner 

 surface of the shell, so that from its examination we may 

 often derive very correct information relative to the inhabit- 

 ant's organization, and some of the most assured characters 

 for distinguishing the genera. You may say to the shell 

 by and bye, when your knowledge is riper, 



" There is a kind of character in thy life 

 That to the observer doth thy history 

 Fully unfold." 



Whenever the edge of the mantle is furnished with any 

 fold or protuberance, with processes or beards, correspond- 

 ing processes on the shell declare the fact; and these pro- 

 cesses are cast in the form of cases for the protection of the 

 fleshy parts they represent. If the original make of the 

 mantle continues during life invariably alike, the surface of 

 the shell is conformable and uniform, either smooth and 

 even, or marked with striae and ridges that extend from the 

 apex to the edge in uninterrupted lines. You may easily 

 satisfy yourself of this by examining the collar of the com- 

 mon snail, which is as even as its shell, and the edge of the 



stationary until the new half volution is formed ; a fact, he says, which is 

 proved by an examination of the shell, and evidenced by the varices being 

 constantly disposed on the two opposite sides. I have heard this opinion 

 maintained by conchologists, but it cannot be even discussed by those 

 who have studied the theory of the formation of shells. Sowerby and 

 Deshayes have animadverted on the hypothesis of Lamarck sufficiently. 

 Gen. of Rec. and Fossil Shells in verb. Ranella : Lam. Anim. s. Vert. 2nde 

 edit. ix. 538. 



DD * 



