494 



Correspondence. 



[October 



as well as the Trochili and Caprimulgi. This order Cypf^eli would stand 

 between the Trochili and Passeres. but as I am soon to have mv second 

 contribution to this subject in hand, all such questions will therein be 

 considered. 



I have a large collection of alcoholics now at my disposal, and am only 

 waiting to secure a better assortment of the Niyhtjars and Trogons before 

 undertaking the work, or rather pushing it, as many of the drawings are 

 already completed. 



In the mean time, permit me to say to those who may be interested in 

 this subject that 1 deem it quite a possible thing that an offshoot may have 

 taken place from the common stock Passeres, near the Swallows, as would 

 in time have produced our typically modern Swifts. I can picture how these 

 forms at first may have had some change in their environment as demand- 

 ed an increase of the power of flight. This would demand an increase of 

 the power of the muscles involved therein, and finally we would find just 

 such changes in tlie bones to which these muscles are attached as we in 

 reality do in existing Cvpseli. So that the enlarged pectorals, the deep 

 keel to the sternum and its unnotched xiphoidal extremity, the short hume- 

 rus of the arm, with its conspicuous processes, are all examples of physio- 

 logical adaftations of structure. So there may have come down to us an 

 entirely different group of birds, as the Hummers, of very different origin, 

 which group may have had the same factor thrown into its environment, 

 somewhere in time, that demanded an increase in the power of flight, and 

 as a consequence we find a similar modification of the parts involved. 

 But when we come to critically examine and compare the modified parts 

 we may find, as we do in the case of the Hummers and Swifts, that 

 although the same end has been very prettily arrived at by the changes in 

 the structures, j'et at the same time quite different forms of the several 

 and corresponding parts had been the result of it all. The first compari- 

 son, Avitlr the views of pointing out the relationships of such, and existing- 

 groups, wherein the fundamental characters are masked by such deceptive 

 similarities, constitute some of tiie most diflicult problems of systematic 

 zoology. In the comparisons, it is In' no means necessary to eliminate 

 them, but simply we must be guided in our conclusions by what the sum 

 of all the morphological characters of the forms under comparison go to 

 show. 



It is really no valid reason that we should retain in the same order, 

 were vessels so classified, two kinds of them, simply because they might 

 both happen to possess "deep keels" and "short shafts" connecting their 

 wheels with their motive powers, for one of these vessels might be driven 

 by steam and the other by some other force, notwithstanding the fact that 

 one might show an additional blade or two in either of its wheels (wings) 

 or perhaps have a difterent style of rudder (tail), and yet the fundamenta 

 difterences be \ery great and justify us in widely separating them in any 

 scheme of classification. 



In conclusion I must express mv satisfaction at finding one who has 

 perhaps thus far tievoled his best energies in avian taxonoiny to the con- 



