Peewee te ee em EMT EE E 
1894.] Development of the Wing of Sterna wilsonii. 769 
bering of the digitsis II, III, IV. In an earlier paper (’66) he 
accepts the numbering I, II and III. Here, too, must be 
enumerated Shufeldt, who states (82, p. 616) that he has 
always adhered to this view, but adds “the fact, however, that 
the first phalanx of the manus of aves is the homologue of the 
pollex of the pentadactyle limb seems to be gaining ground." 
I have not found any further reference to this subject in his 
subsequent osteological contributions further than this usual 
reference to the radial digit as the pollex. 
Mr. Hurst (93) has advocated a third system of numbering 
according to which the digits are III, IV and V. An analysis 
of his reasons will be given immediately when dealing with 
the arguments for the enumeration adopted in the present 
paper. 
The fourth system is that of Tschan (89) who according to 
Zehntner (90) proposes to regard the permanent digits as I, II 
and IV. He bases this on the discovery by Parker (789) of a 
slip of bone in chick, Musicapa and many Galline as occur- 
ing between the second and third of the persisting digits. 
This, says Tschan, is the true digit III. But Parker further 
describes similar slips as occurring on the outside of the “ pol- 
lex" and between the first and second permanent digits as 
well as a true fourth metacarpal on the ulnar side of the hand. 
Tschan suggests that the first of these might be the “ prepol- 
lex" but even with the admission of this doubtful element, 
there would be one superfluous digit. This together with the 
utterly anomalous type of reduction which it presupposes—the 
disappearance of digits in the middle of the manus—is suffi- 
cient to discredit this view. 
That there is developed a fourth digit in the avian manus is 
beyond question, and the fact that this comes upon the ulnar 
side of the three permanent fingers is sufficient to invalidate 
the nomenclature, IIT, IV and V of Hurst. Hurst refers to 
Parker's fourth digit as appearing to be the os pisiforme, and 
since Parker had only the later stages, there would be some 
plausibility in this view. This possibility, however, disappears 
"It was discovered, as Parker points out, long before by Te (’20, pl. IV 
f. 10) in the chick, persisting for sometime as a separate 
