CUVIER. 149 



because they are easy to recognise, tend, however, as 

 pointed out before, ' to the association of very differently 

 organised species, and as often separate into very remote 

 groups of an artificial system two animals which may 

 have very similar anatomical structures.' * 



Cuvier, on the other hand, recognised that the basis of a 

 * natural ' classification could only be found in the anatomy 

 of the animals to be classified. He saw that it was neces- 

 sary to compare animals with one another, not merely as to 

 the possession of some one particular character possibly 

 a character in itself of little real importance but as 

 regards their whole organisation. In this way, by the 

 comparison of each animal in all the points of its structure 

 with every other animal, it was possible to show that 

 certain forms agreed with others as to the ' plan ' of their 

 organisation. In other words, Cuvier established the 

 fact that certain groups of animals could be shown to 

 be built upon the same general plan, irrespective of any 

 modifications which such a plan might undergo ; whereas 

 other groups of animals were built upon a different 

 fundamental plan. Moreover, Cuvier showed that in 

 comparing animals with one another it was necessary to 

 consider only the really essential underlying facts of struc- 

 ture, and that all such structural features as were merely 

 dependent upon adaptation to some particular mode of 

 life should be disregarded. Thus, Linnaeus had grouped 

 the whales and dolphins (Cetacea) with the fishes, the 

 ground of this arrangement being that both the whales 

 and the fishes live in a watery medium, and are there- 



* Owen, ' Lectures on Invertebrate Animals,' p. 9. 



