Chap. I. CONCLUSIONS. 313 



SECTION XIX. 



CONCLUSIONS. 



I have attempted in the preceding sections to ilhistrate, po far as it was in 

 my power, the characters of the order of Testudinata, more with the view of 

 ascertaining what are ordinal characters, than in the hope of drawing a complete 

 picture of the whole order. Consulting the leading works upon this suljject, I 

 have found that all original investigators agree in presenting, as characteristic of 

 this type, the same kind of characters as I have mentioned above, and nearly in 

 the same way, though perhaps they have not aimed so directly, and with the 

 same care, as I have done, at admitting only such anatomical features as are 

 truly characteristic of the whole order, and excluding every feature which occurs 

 in other representatives of the class. If I have succeeded in this attempt, and if 

 the characters presented above are truly those of the order of Testudinata, it follows 

 that ordinal characters are essentially anatomical characters, and not what are 

 commonly called zoological characters. They are borrowed from the peculiar com- 

 plication of the anatomical structure of the class of Reptiles, so that this type 

 furnishes direct evidence of the correctness of the definition of orders given in 

 the first part of this work,^ where it is stated that orders are natural groups, 

 characterized by the degree of complication of their structure. It follows, there- 

 fore, that, to characterize orders correctly, we must compare their anatomical struc- 

 ture with that of the other orders of the same class, as I have done above,^ 

 and that, by this comparison, we ascertain the relative rank of this kind of natural 

 groups; whereas in characterizing families, we consider the structure witli reference 

 to the form of the animal ; and in characterizing classes, we illustrate, in a general 

 manner, the ways in which, and the means by which, the plan of their respective 

 branches is executed. 



The characters of classes, like those of orders, are anatomical ; but in charac- 

 terizing a class, we consider the nature of the different systems of organs which 

 constitute their living frame, we investigate the relations of their systems of organs 

 to one another, their respective functions, etc., and not the various degrees of 

 complication which they may exhibit in these combinations, for such complications 

 constitute ordinal characters. If this is correct, and true to nature, it follows 

 further, that such a distinction as is often made in Natural History, between 



> See Part I., Chap. 2, Sect. 3, p. 150. ^ See Part II., Chap. I., Sect. 3, p. 2J2. 



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