as indicating Affinities of Species. 403 



true affinities^ however, of all which are at once shown by a 

 reference to their moulting. The hag, the lamprey, and the 

 pride, are, thus, extreme approximations of the general verte- 

 brate type of organisation towards the class Mollusca. The 

 Ornithorynchus, among mammifers, approximates very re- 

 markably towards birds ; but it exhibits less analogy with 

 them, collectively, than many rodent species do. The prong- 

 horned antelope is an approximation in its genus towards the 

 Cervidae ; but its affinity to the latter is not greater than in 

 other antelopes. The frigate bird is an approximation towards 

 the eagles ; yet no one would consider it as organised upon 

 the falcon type : so the Pterocles is an approximation towards 

 the pigeons, and the Nicobar pigeon towards the Gallinidae ; 

 each being at once referable to its particular type, though in 

 certain adaptive relations they are intermediate. The pipit 

 genus is a most striking approximation of a very marked type 

 (subordinate to the dentirostral) towards the larks; but its 

 moultings at once intimate its true position in the system, 

 however its general aspect might, at first sight, render this 

 doubtful. It is by no means nearly allied by affinity to 

 ^41auda ; and I will unhesitatingly venture to assert, that by 

 no art could they be induced to unite to the production of a 

 hybrid. 



Analogy^ in the most definite signification of the term, is 

 well exemplified in the close resemblance between the mouth 

 of the swift, and those of the larger high-flying insectivorous 

 bats (Fespertilio). It is exhibited wherever species that are 

 modifications of diverse types are organised to perform nearly 

 the same part in the general economy of nature ; which latter 

 by no means necessarily implies approximation ; as may be 

 illustrated by adducing the vultures among birds, and the 

 dog kind among quadrupeds, or certain of the $phingidae from 

 amongst insects, as compared to the Trochilidse of the feathered 

 race. It is well exemplified by the deadly spring of the cats, 

 as compared with that of the crushing serpents, and as some- 

 what contradistinguished from that of the saltatory spiders ; 

 all the energy of the body being, in the former cases, re- 

 markably concentrated in a single spring, from which 

 exhaustion follows, while in the latter case it is not. It is 

 curiously shown by a. fact related by Sir W. Jardine, of the 

 European howler or eagle-owl (Bubo europse v us), in which the 

 analogy of that genus to the cat family is even more strikingly 

 indicated than by the very remarkable general resemblance in 

 their external aspect. " This bird," observes Sir William, 

 " evinces a great antipathy to dogs, and will perceive one at 

 a considerable distance ; nor is it possible to distract its atten- 



