136 . Psychological Distinctions 



to encounter when occurring beyond the sphere of their 

 adaptations; difficulties which must require human aid, in 

 genera], to render surmountable. But, without re-entering 

 into the details of this subject, it will be sufficiently clear to 

 all who consider the matter, that, were this self-adapting 

 system to prevail to any extent, we should in vain seek for 

 those constant and invariable distinctions which are found to 

 obtain. Instead of a species becoming gradually less nume- 

 rous where its haunts grade imperceptibly away, we should 

 discover a corresponding gradation in its adaptations ; and, 

 as the most dissimilar varieties of one species (those of the 

 dog, for instance) propagate as readily together as individuals, 

 of the same variety, producing offspring of blended charac- 

 ters*, so much so, that human interference is requisite to 

 preserve a breed unadulterated, the unbending permanency 

 of the distinguishing characteristics of all wild animals be- 

 comes of double import. Moreover, the characters in which 

 these differ are of a diverse kind from those observable in 

 any but the most distant of mere varieties ; for they rarely 

 agree in the relative proportions of parts, which are the most 

 fixed of all specific distinctions. It is, therefore, advisedly 

 that we are enabled to state that the raven of the Cape is 

 distinct from the raven of South America; that both are again 

 different from that of the South Sea Islands and from that of 

 Europe. The common jay is diffused over a wide range of 

 latitude, but is the same in Italy as in Sweden : this would 

 not be were it affected by locality or climate; the very trivial 

 distinctions, therefore, which characterise it apart from that of 

 Japan, and from that of Asia Minor, we are warranted in 

 esteeming of specific value. Until the jays of intervening 

 localities present inosculant charactersf, or until precisely 

 analogous diversities are, in wild nature, observed to be pro- 

 duced by locality or climate, the above conclusion is as irre- 

 sistible as it is incontrovertible. 



When, too, we perceive that species so very general in 

 their adaptations as the typical Corvidae are limited in their 

 range, it behoves us to be most cautious in assuming the 

 specifical identity of the most similar animals from widely 

 separated localities. Let it be remembered that no reason 

 can be assigned why those originally distinct should not 



* Individuals of very diverse breeds mostly do so : where the parents 

 more nearly approximate, the young often entirely resemble one or the 

 other. 



•f Here the very remarkable fact, however, is not to be overlooked, that 

 the solitary African species of trogon presents a combination of those 

 colours and markings which uniformly distinguish apart its numerous con- 

 geners in the Oriental isles from those of South America. 



