A HISTORY OE THE NIGHTINGALE. 843 



remarks will apply to Pontia metra (Steph.) ,• and in neither has there been 

 observed any diversity of habits'"' which would warrant the separation of the 

 former from P. brassicce, and the latter from P. rapes. 



But Mr. Blyth seems to think that intermediate forms such as these may have 

 been produced by the admixture of races originally distinct. I cannot admit 

 the probability of this being the case in a natural state ; it appears, on the 

 contrary, highly improbable. And although Mr. Blyth's belief that the offspring 

 of very nearly allied species might be fertile, may be correct, yet it ought to be 

 remembered that the generality of alliances sufficiently close for this purpose, 

 are of species inhabiting distinct geographical ranges, and which are therefore 

 debarred by natural causes from thus intermingling ; and that such closely- allied 

 races, when inhabiting the same locality, " manifest" (to use Mr. B.'s own expres- 

 sion) " no disposition to intermix and blend, as is uniformly the case with even 

 the most distant of true varieties." (Vol. II., p. 457.) It seems probable that, 

 in order to preserve consistency and regularity throughout the animal kingdom, 

 each species has implanted within it an aversion to interbreed with others, which 

 only fails when the influence of natural causes is lost, and that of artificial ones 

 substituted. And when such an intermixture does take place, " the highly 

 curious physiological fact may be borne in mind — which possibly has for its object 

 the continued separate existence of each primitive race — that very closely-allied 

 species, and (as an apparent consequence of the same law) similar varieties, also, 

 less frequently produce, on intermixture, offspring of blended character, than 

 progeny resembling one or the other parent." (Blyth, Vol. II,, p. 457). These 

 facts strongly militate against the possibility of any original races having become 

 blended together. At all events, "probandum est" as Mr. Blyth observes ; and 

 indeed there exists very slight foundation for the theory, which consequently ought 

 not to be allowed any weight in discussing the present question. 



Bewsey House, Warrington, 

 May 19, 1837. 



A HISTORY OF THE NIGHTINGALE.t 



By Edward Blyth, 

 Curator of the Ornithological Society. 



This celebrated and handsome bird (notwithstanding the unobtrusiveness of its 

 colour) is rather longer and more slender than a Robin, which it otherwise much 

 resembles in its figure and proportions. Its colour is plain russet -brown above ; 



* The belief in the existence of a different period of appearance has, I think, been clearly 

 proved to be erroneous; see Vol. II., pp. 128, 129. 

 t Read before the Ornithological Society, May 5, 1838, J. R. Gowen, Esq., in the chair. 



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