352 NATURAL SCIENCE. Nov.. 



space ; such a course seems to me imperative, if anything Uke an 

 intelligible idea of what follows is to be gained. Throughout I have, 

 whenever possible, compared the various points of importance with 

 similar points in the wing of living birds, by which means we shall, 

 I trust, grasp more thoroughly than heretofore the wonderful simi- 

 larity between the wing of yesterday and that of to-day. In the 

 second part, I hope to consider the various restorations which have 

 appeared since the first discovery of the fossil. 



The fore-limb of the higher vertebrates is pentadactyle, or five- 

 fingered ; thus, then, the manus of the modern bird is deficient in 

 the number of its digits. This deficiency has come about during the 

 specialisation of the organ for the purposes of flight ; it became an 

 interesting problem, therefore, to find out the lines along which this 

 reduction has taken place — that is to say, were the two missing digits 

 lost simultaneously or one at a time ? and perhaps more important 

 still, at what stage in the development of modern birds did they 

 disappear, and which of the five do the three remaining digits 

 represent ? Hitherto, it has been taken for granted that the digits in 

 the wing of existing birds correspond to the pollex, index, and medius, 

 or, in other words, to nos. I., II., III. of the normal pentadactyle 

 manus. This question has lately been raised by Dr. Hurst in the 

 pages of this Journal, and will be discussed at length later. 



With the component parts of a bird's wing my readers are, of 

 course, all familiar ; but I would just remind them that in the adult 

 bird there are but two free carpal or wrist-bones, and these belong 

 to the first or proximal row, while those of the second or distal row 

 have become anchylosed or fused together into one mass, blending at 

 the same time with the bones of the metacarpus or hand. In the 

 embryo, however, we may have as many as seven distinct carpals, 

 and the metacarpal bones are free. Such a stage as this we assume 

 to represent a sometime adult form, and it is not, I think, beyond 

 the pale of possibility that fossils showing some such arrangement 

 may be discovered. 



In how far the oldest known fossil bird, Archaeopteryx, contributes 

 towards the chain of gradations which must have existed we unfortu- 

 nately cannot tell, inasmuch as, though there can be little doubt that 

 the number of digits did not exceed three, and that the metacarpals 

 were not fused together, the carpus is not sufficiently well-preserved 

 to enable us to say anything definite. From the photographs which 

 have been lent me, I fancy I can make out, in one, a large sub- 

 crescentic mass, opposed to the base of the metacarpals, but quite 

 separate from them, and representing a fused row of distal carpals, and, 

 very imperfectly, a radial and an ulnar carpal, with an intermedium, 

 closely appHed to the radiale, between them. In the photograph 

 accompanying this paper, which was taken in a different light, the 

 distal carpal would seem to have fused with the metacarpal bones 

 II. and III., but does not extend to I. Hence, how much is due to 



