222 Brewster on Helmiitthophaga leucohronddalis. 



or abnormal examples; the former hypothesis being decidedly 

 negatived by the fact that all the early plumages of both of their 

 affines are known to be widely different ; while the latter is made 

 untenable by the number of essentially similar specimens that 

 have come under our notice. Only one possible solution re- 

 mains : — that they are hybrids between HelmintJiophaga finus 

 and H. chrysoftera. And in support of this view an additional 

 fact may be pointed out ; viz., that nearly all the known speci- 

 mens have been taken within an area where both these species 

 breeds either together, or in close froximity. The very different 

 combinations of markings and coloring in the two hybrid forms, 

 as restricted, is unquestionably due to a reversal of the parents in 

 each case. That is, one of them is produced by the union of 

 H. finus $ with H. chry softer a 9 ; the other by that of H. 

 chrysoftera $ with H. finus § . Just which combination pro- 

 duces either must for the present remain a matter of conjecture. 

 The logical inference is, perhaps, that leucobronchialis" is the 

 offspring of H. finus $ with H. chrysoftera 9 , for in the 

 case of No. 4,668 we have seen that the black throat and cheek- 

 patches, characterizing /awre^ce? equally with chrysoftera, were 

 eliminated by an assumed cross with the male of finus. But 

 additional facts must be forthcoming before this part of the 

 question can be regarded as settled.* 



Before leaving the Golden-winged Warblers it may be well to 

 dwell a moment on the general bearings of the facts adduced, 

 for it must be evident to all that they have a wider significance 

 than simply showing that finus and chrysoftera interbreed, pro- 

 ducing so-called '^leucobronchialis" and lawrencei." They 

 also show that these hybrid oflspring— at least the females, as in 



*On a former occasion (this Bulletin, Vol. II, pp. 66-68) I bestowed a compound 

 specific name on a hybrid Grouse, thereby adopting a custom followed by certain 

 European ornithologists, notably Mr. Robert CoUett of Christiana, Norway. Since that 

 time, however, correspondence with my friend Mr. Ridgway has coiivinced me of the 

 inadequacy of this form of nomenclature. As Mr. Ridgway pointed out, the hybrid in 

 question was derived from parents of difimnt genera, and hence a due regard for accu- 

 racy would have demanded the compounding of the generic as well as specific titles : 

 the result, it is needless to say, would be an absurdly cumbersome title. As this 

 objection will frequently be met with, and, moreover, in \iew of the fact that such 

 specimens are in the majority of cases of exceptional and abnormal significance, I 

 fully agree with Mr. Ridgway that a distinctive name is not called for. The Smithso- 

 nian specimens of hybrid origin are labeled with the names of . both parents connected 

 by the sign -|-, a method that fully meets the requirements of such cases. 



Brewster on Helminthophaga 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 eacb other. But the case is not without 

 pi'ecedent. As long ago as 1S47, 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, luifertile. Ainong his conclusions the 

 following are especially pertinent to the above connection : 



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

 the wild state, in which state, also, h3'brids are sometimes pro- 

 duced. 



"2. Hybriditj- occurs not only among different species, but 

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

 in both cases. 



"3. Domestication does not cause this faculty, but merely 

 evolves it." 



The Rev. John Bachman subsequently took the matter upt 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 mule 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 otlier of the original species." 



In the latter fact we doubtless have the explanation of such 

 aberrant specimens as Nos. i,3io and 2,630, which uninistakably 

 exhibit a slight and otherwise unaccountable trace of hybrid 

 l^arentage ; and siinilarly it is not unlikely that the yellow breast 

 of occasional specimens oi chrysoftera may be due to a taint of 

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



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

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

 ill, 1847, pp. 203-211. 



tAn 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 Ser., 

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



