408 ME. E. DEGEN ON ECDYSIS. 



remiges I.-IY., witli the further definition, however, of a former " metacarpal " 

 derivation. 



The following scheme will be found to supplement the original distribution of the 

 flight-feather elements on the fore limb of the ancestral bird, according to the evidence 

 adduced in its favour through this work. It represents the left-side wing. 



Revised Scheme for the Derivation of the Flifjht-feathers from the Tetradactijle 



Ancestral Form of Birds. 



Proto-metacarpo-diriltals = llypo-metacar^io-difjitals = 



FLIGHr-l'EATHKRS OF PHALANGEAL Ol:IGlN. FlIGHT-FEAIHEHS OF MillACARPAL OllIGlN. 



Digit I. 



Suppressed (lost). Present Pennoe poUicis IV.-I. 



Digit II. 

 Present Metaoarpo-digitals XI.-VI. Present Intercalary row I. -VI. 



Digit III. 



Present Metaoarpo-digitals V.-I. Present Cubital Group II., Secondary llemiges (0) I-I7. 



Digit IV. 



Present Cubital Group III., Secondary Kemiges V.- Present Cubital Group I., Secondary Remiges YIII.-X. 

 VII. — Cubiti veri Xl.-.r. 



DiEF.CTioN OF Moult. 



From the foregoing scheme it may be observed that there are no flight-feather 

 equivalents allotted to the phalangeal portion of Digit I., in which part they figure as 

 " suppressed." 



Such a condition is quite conceivable and in perfect accord with suppression of 

 quills in other portions, as, for instance, the reduction on the extreme phalanx of the 

 second finger from 12 to 11 (Podicepidee, Pelargi, &c.), and from 11 to 10 and 9 in 

 Passeres (Gadow, 21, pp. 656 &c.). This tendency towards a part-suppression, if 

 carried further, would have the effect of leading to total apoptilism. It, moreover, 

 must have proceeded contemporaneously with the feathering of the forearm and was 

 still in progress after, as is evidenced in the Passeres, where it has reached the 

 present climax in the Oscines proper. 



Considering the genealogical relative shortness of Digit I., coupled with the fact of 

 a still greater reduction of size in the present forms of birds to one compound element, 

 there is a strong probability existing that, during the course of the fusion of the 

 phalangeal segments of this digit with its originally independent metacarpal bone. 



