1G8 NATURAL HISTORY OF 



consequently, are forms of mere varieties, or of raws of one 

 common species!"* The second, on the contrary, while admit- 

 ting the minor distinctions, as the effects of local causes, 

 regards the structural, taken together with the moral and intel- 

 lectual characters, as indications of a specific nature not refer- 

 able to such causes, albeit the species remain prolific by 

 inter-union, which, according to them, are the source of varie- 

 ties and intermediate races. 



In systematic zoological definitions, the first may be regarded 

 as sufficiently true for general purposes of classification ; but, 

 physiologically, it cannot be assumed as positively correct, since 

 there are notable exceptions, most probably in all the classes of 

 the animal kingdom, from the lowest up to the most compli- 

 cated ; and, therefore, when applied to mankind, it is of little 

 weight, since even the exceptional law, assumed by the writer 

 who regards the human races as necessarily of one species 

 only, is more likely to operate in the usual generical form of 

 animated beings, than by acting inversely, granting to one spec- 

 ified type the attributes that belong, in all other instances, to 

 a genus; and so far supporting his own doctrine of a progress- 

 ive creation. In physics, dogmas are admissible only so long 

 as they are not disproved. Since the fissiparous propagation of 

 some animals is established, " Omne animal ex ovo " is no 

 longer asserted to be a universal maxim, nor that all parturi- 

 tion of mammalia is derived wholly from uterine gestation; 

 for, without referring to classes of a lower organization, fertile 

 offspring is obtained among several genera of brute mammals, 

 from the union of two or more so-called distinct species ; or 

 the definition of that word is several ways incorrect. Frederic 

 Cuvier, sensible of the fallacy embodied in the maxim above 

 quoted, endeavored to prop it up by an argument drawn from 

 the asserted gradual decrease of prolific power in a breed of 



* Buffon and Cuvier have made their definitions somewhat more com- 

 plicated, but essentially the same 



