CHAP. XIV.] ANALOGICAL RESEMBLANCES. 351 



tinct Swedish turnip. The resemblance between the greyhound 

 and the racehorse is hardly more fanciful than the analogies which 

 have been drawn by some authors between widely different 

 animals. 



On the view of characters being of real importance for classifi- 

 cation, only in so far as they reveal descent, we can clearly under- 

 stand why analogical or adaptive characters, although of the 

 utmost importance to the welfare of the being, are almost value- 

 less to the systematist. For animals, belonging to two most 

 distinct lines of descent, may have become adapted to similar 

 conditions, and thus have assumed a close external resemblance ; 

 but such resemblances will not reveal will rather tend to conceal 

 their blood-relationship. We can thus also understand the ap- 

 parent paradox, that the very same characters are analogical 

 when one group is compared with another, but give true affinities 

 when the members of the same group are compared together: 

 thus, the shape of the body and fin-like limbs are only analogical 

 when whales are compared with fishes, being adaptations in both 

 classes for swimming through the water ; but between the several 

 members of the whale family, the shape of the body and the fin- 

 like limbs offer characters exhibiting true affinity; for as these 

 parts are so nearly similar throughout the whole family, we" 

 cannot doubt that they have been inherited from a common 

 ancestor. So it is with fishes. 



Numerous cases could be given of striking resemblances in 

 quite distinct beings between single parts or organs, which have 

 been adapted for the same functions. A good instance is afforded 

 by the close resemblance of the jaws of the dog and Tasmanian 

 wolf or Thylacinus, animals which are widely sundered in the 

 natural system. But this resemblance is confined to general 

 appearance, as in the prominence of the canines, and in the 

 cutting shape of the molar teeth. For the teeth really differ 

 much : thus the dcg has on each side of the upper jaw four pre- 

 molars and only two molars; whilst the Thylacinus has three 

 pre-molars and four molars. The molars also differ much in the 

 two animals in relative size and structure. The adult dentition 

 is preceded by a widely different milk dentition. Any one may 

 of course deny that the teeth in either case have been adapted 

 for tearing flesh, through the natural selection of successive 

 variations ; but if this be admitted in the one case, it is unintelli- 

 gible to me that it should be denied in the other. I am glad to 

 find that so high an authority as Professor Flower has come to 

 this same conclusion. 



The extraordinary cases given in a former chapter, of widely 

 different fishes possessing electric organs, of widely different 

 insects possessing luminous organs, and of orchids and ascle- 



