404 External Changes in Birds, 



tion so long as the animal remains in sight. When first per- 

 ceived, the feathers are raised," &c., exactly as a cat raises 

 her fur at sight of her natural enemy ; though, in either case, 

 it is difficult to say why they should be inimical. No doubt, 

 however, the purpose, the reason for this antipathy, is the 

 same in both instances, and it is for the naturalist to endeavour 

 to find it out. The common pipit, a modification of the den- 

 tirostral type ; and the Lapland snowfleck, one of the coni- 

 rostral (as here limited) ; are in so far related to each other 

 by analogy, as that they are both approximations towards the 

 lark genus, an extreme modification of the omnivorous or 

 corvine type ; they are therefore related to each other by a 

 certain analogy ; to ^41auda, by approximation ; and to all the 

 members of their respective separate groups, by an additional 

 degree of affinity to what subsists between either of them 

 and the others. Affinity and analogy, of course, coexist, as 

 all organisms are, at least, related by what I have termed the 

 first degree of the former ; but the extent of the former does 

 not necessarily affect that of the latter : vultures and dogs, 

 for instance, are allied by three degrees of affinity ; while the 

 carrion beetles (Carabidae) are related to either by only two 

 degrees : yet the analogy is as great in the one instance as in 

 the other. Pure analogy may subsist with very trifling ap- 

 proximation ; as is shown by the already cited case of the 

 cats and serpents, or as may be exemplified by a hundred 

 similar instances of corresponding groups existing in major 

 divisions of diverse structure, in which, however marked the 

 analogy, however similar the office they were destined to 

 perform, the degree of approximation is in many instances 

 quite imperceptible. 



Affinity, approximation, and analogy, may therefore be col- 

 lectively defined as pertaining to the physiological relations 

 subsisting between different species, as opposed to their 

 adaptive relations; of which latter they are wholly independent: 

 that is to say, different species, nearly allied by either of these 

 physiological relations, exhibit no mutual, no relative adapta- 

 tion towards each other's habits and structure; such as we 

 observe in the huge claws of the anteater (Myrmecophaga), 

 evidently furnished in direct relation to the habits of a parti- 

 cular group of insects, the mounds of which they are obvi- 

 ously intended to scrape open, while the tongue is as expressly 

 modified to collect the aroused inhabitants, upon which alone 

 the creature is fitted to feed, and upon the supply of which, 

 therefore, as an existing species, its being altogether depends. 

 Adaptive relations are, in general, even more obvious and 

 striking in groups which are physiologically the most widely 



