of certain Birds of Cuba. 13 



M. Cuvier, that the natural history of an animal is the know- 

 ledge of every thing that regards that animal, — then Natural 

 History, as a science, is only studied in effect when we are 

 engaged in the pursuit of the natural system. It is not, there- 

 fore, so much the difference between organs, that we ought to la;y 

 stress upon, as the mode in which they vary ; from which truth 

 arises another, namely, that in those groups where the variation 

 of an organ is at its maximum, — or, in other words, where the 

 differences between the various states of an organ are the most, 

 — there such an organ is of less consequence as a principle of 

 division characterizing large groups ; for it is the mode of vari- 

 ation that we ought to attend to. Thus in the Natatores, the 

 number of cervical vertebrae is at its maximum of variation ; 

 in the Grallatores, the form of the beak is at its maximum of 

 variation ; in the Rasores, the number of lumbar vertebrae ; in 

 the Insessores, the economy and nature of food ; — and so on. 

 The primary divisions, therefore, of these several large groups of 

 birds, will not depend upon the above respective circumstances, 

 although by tracing the variation of them we are enabled to 

 apply corrections to the place that may have been assigned 

 each species from other considerations, as close to its next of 

 kin in natural affinity. 



Generally speaking. Mammalia have more vertebrae in their 

 spine than Birds : but this is scarcely to be imagined a mark of 

 their superior perfection ; for man, undoubtedly the chief of 

 Mammalia, has one of the lowest numbers of vertebrae that the 

 class presents. The variation of the number of vertebrae in 

 Mammalia is not at all conducted on the same principles as that 

 in birds : in the latter class this number varies in every possible 

 way, yet on the whole is tolerably regular in its variation. In 

 Mammalia the number in some respects, such as that of the ver- 

 tebrae of the cervix, is almost constant ; and yet with respect 



to 



