182 PROCEEDINGS OF THE ACADEMY OF 



nus was ever unispecific, and has since by whatever causes been made other- 

 wise by differentiation of several phases, then linaiius was perhaps the actual 

 type of the genus. But as at such time the genus was then rather forming 

 than formed, it is more probable that the characters of linarius (i. e., of ^Effio- 

 ihus in its entirety) were then specific only in relation to such types as Linola, 

 Leucoslicte., Chnjsomitris, &c. So at any given moment in bird-life, a generic 

 type or plan is an ideal induction of ours, rather than a material existence. 



It is true, nevertheless, that at present Unarms is the most common and 

 widely distributed aspect of j:'Egiolhus, and that it comprehends a larger per 

 centum of j.Egioihus than any other form. Were it the only phase of ^■Ec/iothiis 

 now living, we could handle the genus in much the same manner as we shall 

 have occasion to with consideration of other forms. I shall for the present 

 assume that linarius is ^Egiothns, and see if it is possible, upon this hypothesis, 

 to account for the balance of ^E'^w^/ms that are now living more rationally 

 and naturally than they can be accounted for upon any other premise. 



It is specifically characteristic of the " typical" (f. e., normal, or most usual 

 and general) ^«w(n-2i/s to be, 1, under six and not under five inches long ; 2, 

 with a wing 2-75 — 3-00 inches long; 3, a tail 2-25 — 2-65 inches long; 4, a 

 tarsus equal to the middle toe and its claw ; 5, a bill compressed-conic, very 

 acute, with not appreciably curved culmen, and never wholly yellow or 

 wholly blackish ; 6, the light and dark streaks of the back about equal in 

 amount, and mingled with an intermediate color; 7, the rump never wholly 

 unstreaked, yet always lighter than the back; 8, the male sex indicated by a 

 bright color on the breast and rump that is between deep crimson and pale 

 rose, yet not reaching, under mature conditions, either of these extremes. 



It is to be observed, in the first place, that a large per cent. — perhaps -50 or 

 more — of ^^?o/'/hm have preserved these special conditions inviolate. Upon 

 these birds neither geographical regions, latitude, longitude, climate, or any 

 other perturbating influences have exercised the slightest appreciable effect. 

 Specimens from all parts of Europe, from Hudson's Bay, New York, Southern 

 States, Kansas, Oregon, Sitka (and Asia?), may be found as closely resembling 

 each other as birds from the same nest ever do. In short, there are no differ- 

 ences. As similar ^-Eyiothi as I ever compared were from, respectively, Ger- 

 many and the Rocky Mountains ; and probably more than half the specimens 

 at present existing in all the collections in the world will be found thus cor- 

 related. So it is a fact that, whatever influences have been brought to bear 

 upon ^Egiotkus, tending to produce, or producing its differentiation or forking 

 into several recognizable channels, such influences have been nilin effect upon 

 most individuals. 



This is the first broad fact to be remembered. It is not an isolated one. On 

 the contrary, it is one of a parallel series of large extent. In the cases of a 

 number of l3oreal and arctic types, as Ngclea, Suriiia, Finicola, Ampelis sp., and 

 Plectrophanes sp., among land birds, and still more among natatores, as the 

 glacial Lacidm, Anatidte, Alcidrr, &c., we find the Nearctic the same as the Palne- 

 arctic; and generally, the more nearly circum-polar tj^pes are, the more likely 

 it is, aeieris parihi/.f, that distinctions between these two regions will be re- 

 duced to zero. It is to be observed, further, that linarius, besides being in 

 longitude the most widelj' dispersed phase of ^Egiothus, is at the same time 

 the most restless element of its genus. It has properly no special abiding 

 place ; its movements are irregular, almost spasmodic ; it is found as far north 

 as most, if not' any, other forms ; and, at least in the United States, ranges 

 further south than any. I think it probable that the clue to its singular con- 

 stancy is to be found in this fact: individuals not being subjected through 

 series of generations to precisely the same climatic and other influences, in 

 consequence of which the equilibrium, so to speak, is preserved, and variation 

 in this or that special direction opposed. This inference seems just, and is 

 corroborated by the fact, about to appear, that the more geographically re- 



[August, 



