Brewster on Hclminthophzga leucobronchialis. 223 



the case of No. 4,667 — reproduce with at least one, and prob- 

 ably either of the parent species ; if not — as is by no means 

 impossible — with each other. But the case is not without 

 precedent. As long ago as 1847, Dr. Samuel George Morton, 

 in the course of an essay on the subject of hybridity* cited 

 several well-authenticated instances of the interbreeding — often in 

 a wild state — of various European Finches. A yet more remote 

 alliance, given on the authority of M. Vieillot, was that of a 

 Canary and a Nightingale, the single egg resulting from their 

 union proving, however, unfertile. Among his conclusions the 

 following are especially pertinent to the above connection : 



" 1. A latent power of hybridity exists in many animals in 

 the wild state, in which state, also, hybrids are sometimes pro- 

 duced. 



"2. Hybridity occurs not only among different species, but 

 among different genera ; and the cross-breeds have been prolific 

 in both cases. 



kk 3> Domestication does not cause this faculty, but merely 

 evolves it." 



The Rev. John Bachman subsequently took the matter upf and 

 supported the negative side of the question, but while be severely 

 criticised Dr. Morton's views we find him admitting (p. 169), 

 *'That in a very few species a progeny has been produced that 

 was incapable of propagating with the half-breeds, — in other 

 words, that the hybrid male was physically incapable of having 

 offspring with a hybrid female ; hence the latter had to resort to 

 the full blood of either species, and thus the intermediate breed 

 returned to one or the other of the original species." 



In the latter fact we doubtless have the explanation of such 

 aberrant specimens as Nos. 1,210 and 2,620, which unmistakably 

 exhibit a slight and otherwise unaccountable trace of hybrid 

 parentage ; and similarly it is not unlikely that the yellow breast 

 of occasional specimens of chrysoptera may be due to a taint of 

 ftinus blood. The impaired sexual vitality — granting, for the 



* " Hybridity in Animals and Plants considered in reference to the Question of the 

 Unity of the Human Species." American Journal of Science and Arts, 2d Ser., Vol. 

 Ill, 1847, pp. 203-211. 



t An Investigation of the Cases of Hybridity in Animals on Record, considered in 

 reference to the Unity of the Human Species. Am. Journ. Sci, and Arts, 2d Set., 

 Vol. V, 1848, pp. 168-197. 



