ARRANGEMENT OF ANIMALS. 85 



Moreover, under certain circumstances, with which we 

 are not well acquainted, a more important change of orga- 

 nization occurs. A new character springs up, and is pro- 

 pagated by generation : this constitutes a variety, in the 

 language of naturalists. The number and degree of these 

 variations are confined within narrow limits ; they occur 

 chiefly in the domesticated animals, and have not interfered 

 with the transmission and continuation of those forms which 

 constitute species. They will be more particularly consi- 

 dered hereafter. 



Proceeding then, on the criterion of definite form, trans- 

 mitted by generation, we may define a species as a collec- 

 tion of all the individuals which hixve descended one from 

 the other, or from common parents, and of all those which 

 resemble them as much as they resemble each other*. 



Thus, our first operation, in classifying the animal king- 

 dom, consists in referring individuals to their species. The 

 next brings together the species most nearly resembling 

 each other, and forms them into groups, called genera* 

 This presupposes a thorough knowledge of the animals ; 

 because the species included under each genus should 

 resemble each other more closely than the species of any 

 other genus. For example, the lion, tiger, lynx, leopard, 

 panther, cat-species, with some others, compose the genus 

 felis or cat. All these have a savage character, as they 

 prey on living animals. For this purpose they are armed 

 with powerful teeth, with great muscular strength in the 

 jaws, neck, and limbs : they all have the tongue and glans 

 penis covered with sharp, horny prickles ', and they are 

 furnished with curved, sharp, and cutting nails or claws, 

 which, by a peculiar mechanism, are retracted, so as not to 

 press against the ground when the animal is not employing 

 them. Thus the species in question all agree in the leading 

 points of organization ; and they agree likewise in general 

 habits and character. The common cat is the only one 

 actually domesticated; but the lion, tiger, and others, are 



* CuviEi'., Regnc Animal; t. i. Intn>ductioii, p. 19. 



