i894. THE WING OF ARCH^OPTERYX. 359 



climbing ; but as soon as the proximal feathers have increased 

 sufficiently to serve to break the force of a fall, should such occur, 

 the remaining distal feathers begin to develop ; at the same time, the 

 hand begins to shorten, till, as will be seen in Fig. III., in the adult 

 the hand has come to be shorter than the forearm, the claws have 

 disappeared, the thumb no longer extends to the level of the III. digit, 

 nor does the II. project beyond the posterior wing-fold, the bird now 

 being able to move from one place to another by flight instead of by 

 climbing. In the course of development, I imagine the species has 

 managed to shorten the hand and lose the claws as soon after they 

 ceased to be of assistance as possible ; but could we discover a yet 

 more primitive form it is probable that we should find that the claws 

 and long hand were retained throughout life. 



The common fowl, being a more recently-evolved form which 

 has exchanged its arboreal for a terrestrial habit, is gradually elimi- 

 nating this phase in the life-history. The hand of the nestling is still 

 longer than the forearm, though not much ; but the II. digit is scarcely 

 produced beyond the wing membrane and the claw has been lost 

 though present in the embryo, the poUex has retained the claw, and 

 extends just up to the III. digit. The arrested development of the 

 quills, however, still persists, and apparently Jor the same period as 

 that in Opisthocomus, though it has long since ceased to have any 

 function. 



If we are to believe that birds have been derived from an arboreal 

 ancestor, then Opisthocomus proves to be a bird of most exceptional 

 interest, for it is probable that the peculiar habits of the nestling 

 may be a survival of an order of things handed down from the very 

 dawn of avian development. 



If these speculations have any value, will it seem too great a 

 demand upon the imagination to suggest that the claws in 

 Archaeopteryx were of prime importance only during the nestling 

 period, and that their presence in the adult may be rather due to the 

 fact that they had not " had time," so to speak, to erase them after 

 they ceased to be functional, as Opisthocomus has succeeded in doing 

 to-day ? Possibly they may have been used by the adult on rare 

 occasions, but surely it is doubtful. 



The view that my readers take with regard to this matter will 

 depend entirely upon their conception of the power of flight of 

 Archaeopteryx. Generally speaking, it is probable that it has been 

 considerably underrated. Perhaps undue anxiety to enhance the 

 value of Archaeopteryx as connecting link between the Reptiles and 

 Birds has done not a little to warp the views of many of those who 

 have expressed an opinion on the subject. Usually, if we ask for 

 some sort of estimate of the flight of this ancient bird, we are 

 referred to flying lizards and flying squirrels — unsatisfactory com- 

 parisons. 



Judging from the relative size of the wing as compared with the 



