224 Brewster on Helminthophaga leucobronchialis. 
sake of argument, that it is always impaired in such cases — of the 
original hybrids, would soon be restored by this breeding back 
into one of the parent stocks, and the descendants would hence 
stand a good chance of being numerous, while it would certainly 
require the succession of many generations to wholly eliminate 
the traces of their mixed ancestry. And if this state of affairs 
exists in one genus of birds, why may it not be looked for in 
others? There are some puzzling instances of the occasional 
cropping out of respective characters among allied but apparently 
perfectly distinct species which cannot be explained by any of the 
known laws of geographical variation. The possibilities opened 
by this field are bewildering, but for the present we are safer to 
lay them aside and apply the direct analogy furnished by the case 
of the Helminthophagce to a few obviously similar ones. 
Until very recently there was not a single established example 
of hybridity among North American Passer es, and many of our 
leading ornithologists were incredulous as to its occurence in a 
state of nature save among the Grouse and some of the Swimming 
Birds, while no one seems to have considered the possibility of its 
explaining some of the standard puzzles* that have been handed 
down to us by Audubon and other of the earlier ornithologists. 
But Mr. Trotter’s hybrid Swallow (described in Vol. Ill, pp. 135, 
136 of this Bulletin) gave us an undoubted instance, and now we 
have startling evidence that some of the Helminthophagce f have 
been regularly* contracting misalliances under the very noses of the 
scientists who were insisting that such things could not be. Who 
can say where this entirely irregular state of affairs will' be found 
to end ? Cuvier’s Kinglet, with its Vermillion crown-patch bor- 
dered by black stripes , its black eye-stripe and white wing- 
* From a review in a recent number of “ Nature ” I learn that Mr. Seebohm in his 
late work on the Turdidce, forming Vol- V, of the “ Catalogue of the Birds of the 
British Museum,” has lately recognized hybridity as accounting for certain obscure 
Old World species ; but up to the time of placing the present article in the printer’s 
hands I have been unable to obtain a copy of his book or to ascertain the precise 
nature of his investigations. 
f Mr. Ridgway has lately shown (this Bulletin, Vol. V, p. 237) that Helminthophaga 
cincinnatiensis , Langdon (originally described in Jour. Cin. Soc. Nat. Hist., July, 1880, 
pp. 119, 120, PI. VI — description and plate reproduced in this Bulletin, Vol. V, pp. 
208-210, PI. IV) perfectly combines the characters of Helminthophaga pinus with those 
of Oporornis formosa. If, as seems highly probable, he is right in considering it a hybrid 
between these species, it affords another striking example of the tendency of H. pinus 
to seek alien connections. 
