Early Development of Appendicular Skeleton of the Ostrich. 359 



one another more closely than would appear from the figures. 

 From his figures 258 and 259 there would appear to be a large 

 radiale and a small ulnare as in the ostrich. But in those of 

 the earlier stages he seems to interpret the appearances otherwise. 

 He has failed to discover the fourth metacarpal. 



There are one or two points in the structure of the early ostrich 

 manus of considerable interest. The presence of four digits has 

 previously been known in other forms. Leighton has figured various 

 stages of the manus of Sterna showing the four digits, and there can 

 be little doubt that the four in Sterna are the same as the four in 

 Struthio. Whether these are to be regarded as I., II., III., IV., or 

 II., III., IV., V., as Leighton seems to believe, might be discussed at 

 some length, but the condition of affairs in Archceopteryx appears to 

 conclusively settle the matter. There can be little doubt that the 

 three-clawed digits of Archceopteryx are homologous with the three 

 well- developed digits of the manus of the higher bird, and there can 

 be as little doubt that these are I., II., III. from the phalangeal 

 formula being 2, 3, 4. Kitchen Parker has also shown that in the 

 manus of the chick the number of the phalanges proves the first two 

 digits to be I. and II. It seems unnecessary to discuss the remark- 

 able view of Hurst that Archceopteryx had five digits in the manus 

 and that the digits that are preserved in the higher avian manus are 

 III., IV., and V. The fact that the first and second digits have 

 never more than 2 and 3 phalanges, and from their bearing claws 

 are manifestly not degenerate, seems to me conclusive on the 

 subject. 



Another point of interest is the curious circumstance that the 



ulnare is differentiated earlier than the other carpal elements and 



also that the rudimentary fourth metacarpal is relatively larger at 



10 days than at 11 days. From this we are perhaps justified in 



concluding that the fourth digit in the ancestor of the bird was well 



developed. 



Pelvis. 



The structure of the pelvis of the adult ostrich has long been 

 known. In 1872 Garrod and Darwin discovered, in addition to the 

 well-known elements, a small bone attached to the front of the pubis. 

 This they believed to correspond to the " marsupial bone " of the 

 lower mammals. Mivarfc, in his work on the ostrich skeleton, also 

 refers to it, but expresses no opinion as to its homologies. In most 

 text-books no reference is made to it, though Beddard mentions it 

 and considers that it is conceivably a " marsupial bone." 



The very early condition of the avian pelvis has been studied by 

 Alice Johnson in the chick, by Mehnert in Larus, and by Jeffery 



