A HISTORY OF THE NIGHTINGALE. 
843 
remarks will apply to Pontia metro, (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. rapce. 
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, u 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 NIGHTINGALES 
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. XL, pp. 128, 129. 
t Read before the Ornithological Society, May 5,1838, J, R, Gqwen, Esq., in the chair. 
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