(58 INTRODUCTION. 



entific certainty and exactness require characters which 

 are not liable to change, and which we can seek only 

 in the organization of the animal. This alone remains 

 always the same ; for notwithstanding the speculations 

 of M. Lamarck and his followers, there is not a shadow 

 of evidence tending to prove the slightest permanent 

 change, in the structure of a single animal, since the 

 creation of the world. Species, genera, and even whole 

 groups of animals have been created, and have be- 

 come extinct ; but, so far as we know, the organization of 

 the most insignificant species has undergone no change. 

 The permanent characters drawn from this source, 

 combined with those of the shell, wiU enable us success- 

 fully to discriminate between species, and we may ob- 

 tain collateral aid from the observation of their struc- 

 tural functions, their uistincts, and their habits ; and 

 thus, while seeking to exliibit their distinctions alone, 

 may do much towards completing their natural history. 

 The requirements of science can no longer be satisfied 

 by a single Linngean phrase ; the characteristics of the 

 whole organized being are needed ; and the description 

 of the shell alone, ought never to be admitted, except 

 when that of the animal itself cannot be obtained. The 

 naturalist who has it in his power to acquire a know- 

 ledge of the animal, as well as of the shell, should be 

 held in every case so to do, and to make both known 

 together. 



Conchology, considered as the study of the imper- 

 ishable portions of a class of animals, has been, and 



