ANALOGICAL RESEMBLANCES. 441 



ened stems of the common and specifically distinct Swedish 

 turnip. The resemblance between the greyhound and the 

 race-horse 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 

 classification, only in so far as they reveal descent, we can 

 clearly understand why analogical or adaptive characters, 

 although of the utmost importance to the welfare of the 

 being, are almost valueless to the systematist. For animals, 

 belonging to two most distinct lines of descent, may have 

 become adapted to similar conditions, and thus have as- 

 Bumed a close external resemblance; but such resemblances 

 will not reveal — will rather tend to conceal their blood- 

 relationship. We can thus also understand the apparent 

 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 to- 

 gether: 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 ances- 

 tor. So it is with fishes. 



Numerous cases could be given of striking resemblances 

 in quite distinct beings between single parts or organs^ 

 wiiich 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 cut- 

 ting shape of the molar teeth. For the teeth really 

 differ much: thus the dog has on each side of the 

 upper jaw four pre-molars and only two molars; while 

 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 



