314 AMERICAN TESTUDINATA. Part II. 



anatomical and zoological characters, is not correct, in the sense in which it is 

 generally understood ; but that so-called anatomical characters are either characters 

 of the classes or of the orders, and, to some extent also, of the families, while the 

 so-called zoological characters are more properly generic or specific characters, and 

 the features generally considered in what is now called Philosophical Anatomy, and 

 in Morphology, are mostly characters of the great types or branches of the animal 

 kingdom. The separation of Comparative Anatomy from Zoology, as a distinct 

 branch of science, is therefore only justifiable in so far as the proper meaning 

 of those peculiarities of the structure of animals which characterize classes or 

 orders, or families or genera, have not yet been satisfactorily ascertained ; but I 

 look forward to the time when the more comprehensive groups of the animal 

 kingdom shall be illustrated in our zoological works with that fulness of struc- 

 tural illustrations which is now generally supposed to belong to anatomical works 

 only, and with that searching care which alone can insure a proper discrimination 

 between organic features of diflFerent kinds. 



Such a method will, in due time, relieve our science of all the exaggerations 

 respecting homologies, with which it has of late been incumbered. As soon as it 

 is understood, that the great branches of the animal kingdom are characterized by 

 different plans of structure, and not by pecuUar structures, we shall have fewer of 

 those unsuccessful attempts to force every peculiarity of every type into a dia- 

 gram, by which, renouncing almost entirely the study of the wondei'ful combina- 

 tions of thought which are manifested in the endless diversity of hving beings, 

 authors substitute for them a dead formida of their own making. Having once 

 understood, for instance, what constitutes the pecuhar plan of Vertebrates, we shall 

 be prepared to find it executed in a variety of ways and with innumerable com- 

 plications, and we shall no longer try to force the framewoi^i of a Fish into a Pro- 

 crustean bed, to which we may reduce at the same time all other Vertebrates, with 

 Man. When the axis of the body consists of a simple dorsal cord, we shall be 

 willing to acknowledge that it is not to be considered as an articulated backbone ; 

 Avhen the skull-box consists of a continuous cartilage, that it is not to be artificially 

 divided into isolated parts ; and, when there are no limbs at all, we shall not 

 assume that they exist potentially in the same degree of comjilication as in animals 

 more flivorably endowed. And, let it not be supposed, that such a sobriety of 

 views excludes general comparisons ; it only withdraws them from the field of 

 fancy to the rich field of hfe. 



Suppose, for a moment, that we should attempt to homologize the different 

 parts of the solid shield of a Turtle with the complicated system of muscles which 

 intervene between the ribs and the skin in the trunk of other Vertebrates, or 

 assume, perhaps, that the few scales which cover their back are to be considered 



