4760 Notices of New Books. 



it in species. Yet, we may ask, on what characters, excepting those 

 of the shell, were those very genera founded which he adopts through- 

 out his work ? and if we are right in supposing that these genera were 

 founded on characters of the shell alone, and are serviceable in a 

 system dependant alone on the characters of the animal, does not this 

 coincidence not only prove that the characters of shell and animal vary 

 in unison with each other, but that the shell is a most important guide 

 when the animal is injured, imperfectly preserved, absent or altogether 

 unknown ? We wish to know so much of nature, and really know so 

 little, that we should rejoicingly avail ourselves of every assistance she 

 may offer. 



We must, however, confess to a great leaning towards that principle, 

 which, indicated in everything Mr. Clark has written, tends to elevate 

 physiological over physical characters as the basis and starting-point 

 of system ; and we behold, in imagination, the dawning of a new era 

 in science, to be distinguished by a refertnce to causes rather than a 

 studying of effects; by an observation of functions rather than of 

 organs ; by noting the stages by which a being arrives at maturity 

 rather than by the mensuration of parts when mature. The idea, how- 

 ever, although, as we have said, indicated in all that Mr. Clark has 

 written, does not originate with him ; Adanson, Lamarck, Poli, De 

 Blainville, Gray and Swainson have done much the same thing, 

 making physiological characters the foundation of their several 

 systems. It does, however, become a most important question, and it 

 is one on which we range ourselves among the non-contents, whether 

 the shell, which we are content to throw over in the classification, is 

 also to be ignored in the discrimination of species. To us it seems, 

 as the colouring of the bird, as the striping and spotting of the cat 

 tribe, useless in the formation of primary groups, but all-important in 

 the discrimination of species. A word more : Mr. Clark's terms are 

 not sufficiently definite and precise; he is either careless in phrase- 

 ology, or adopts technicalities of which he does not know the exact 

 import: thus, in the very outset, his system, founded on sexual 

 organization, is rendered obscure, by his using the word "dioecious" 

 in a sense exactly opposed to the received one : this fault is not un- 

 common among those authors who go somewhat ahead of the rank 

 and file of their brother naturalists, but it is nevertheless a grave one. 

 lie who promulgates new ideas should be particularly careful to 

 explain them with perspicuity and precision. With these reservations 

 we cordially lecommend Mr. Clark's volume to the study of naturalists. 



