402 MR. E, DEGEN ON ECDTSIS. 



pennancntly associated) deserve to be called " pernuiuent " only in so far as they are 

 derived from the same source as the former. 



All that remains to be further explained now, after having shown their purely digital 

 value, are those digital ]^>halan(jes on which they were originally situated. These could 

 have been none other than those belonging to digit III., as we shall see. 



The crowding together on the wrist of the flight-feathers in their backward- 

 shifting process towards the elbow caused the forearm to receive first the quills 

 originally belonging to digit IV. Next to these followed the " metacarpals " belonging 

 to digit III. This must have occurred contemporaneously with the process of 

 ankylosis of the two metacarpal bones, so that these " digital " remiges in question and 

 belonging to digit III. found the channel obstructed by their former neighbours, the 

 " metacarpals " mentioned above, which had preceded them in this course of shifting 

 into their new position on the forearm and in the latter of which they became fixed. 

 Hence, in the same manner, they became fixed themselves, in turn, on the combined 

 metacarpal bones. 



Another peculiarity which has often arrested my attention also seems to point 

 strongly to such a rearrangement. It is that of primary digital remex VII., or, 

 anatomically speaking, the " addigital," which, instead of having its base inserted, 

 like those of VIII., IX., X., or XI., on the phalanges which bear them, crosses the 

 retained terminal phalanx of digit III. entirely, to insert itself above it, together with 

 the shafts of all those from this one inwards, on the metacarpal bone of digit II. This 

 arrangement is also distinctly shown in Wray's (46) text-figure on p. 351 (fig. 2 a, I. c.) 

 for the faithful drawing of the wing of an adult Ostrich, in which bird, owing to the 

 greater relative length of this complex terminal phalanx, the shafts of no fewer than 

 three primaries likewise cross it. 



A reference also to my former diagram (table i. fig. 3, I. c.) shows that in this I 

 suggested, by means of dotted outlines, a suppositional remex to have been present, as 

 well as that of the "carpal remex and its covert" ; it is marked there I', and X on 

 phalanx I. of digit III. When this digit was probably slightly inferior in length to 

 dio-it II., but otherwise composed of the same number of phalanges (see also Wray, 

 (45), p. 284, "Note on the Vestigial Structure in an Adult Ostrich," figs. 1-4 

 representing the digital phalanges of digit III.), it was doubtlessly, capable of giving 

 accommodation to a similar number of remiges like that composing the inner section 

 of the primaries, as in the present forms of birds. In fact, Wray shows this number 

 to be equal for the Ostrich, namely 8 " metacarpals " and 8 " digitals." 



The next point of difference to account for concerns those flight-feathers on the 

 cubitus which compose Group III., the last to moult, and comprising secondaries VII., 

 VI., and V. In my former drawing the metacarpal bone of digit IV. is represented as 

 carrying one remex only, namely cubital VIII. 



Having seen that IX. and X. also moult in an inward direction, the inference from 



