1888.] DR. H. GADOW ON THE llEMFGES OF BIRDS. G67 



The first finger had already inherited from the Reptiles a tendency 

 towards shortening ; it remained therefore outside the series of the 

 other fingers, and partook of the formation of the wing to a small 

 extent only. The next two metacarpal bones and tiiose of the second 

 finger became elongated and thus anchylosed, because of their contem- 

 porary and one-sided use. The other bones of the middle hand and 

 other fingers were reduced in size and number, since the newly gained 

 and much strengthened axis necessitated their presence no longer ; 

 moreover a fully developed third, fourth, and fifth finger would have 

 much interfere J with the folding of the wing, which is effected by a 

 strong abduction towards the ulnar side. Purely mechanical reasons 

 caused the primaries to grow into quills stronger and larger than the 

 secondaries. In the embryos of many birds the remiges of the fore- 

 arm appear earlier and for some time grow more rapidly than those 

 of the hand, until they are overtaken by the primaries ; thus they 

 still repeat their phylogenetic development. 



Alter the reduction and partial anchylosis of the skeleton of the 

 hand has once taken place it is impossible to redevelop the lost fingers 

 and to free or separate the anchylosed metacarpals again. The wing 

 of the Ratitae does in no way differ from that of the typical Carinatse. 

 Fiirbringer concludes therefore rightly that the present Ratitee are 

 the descendants of birds which once possessed the power of flight. 

 Now their remiges are soft, or, as in Casuarius, have partly lost their 

 vanes, but such soft quills could never have caused the anchylosis of 

 the hand-skeleton. The relatively very considerable size of the 

 whole anterior extremity of Ostrich embryos is an additional support 

 to this view. In a similar way the length of the humerus ot the 

 Eocene Palceeudyptes is a weighty reason against the separation of 

 the Penguins from the other Carinatse. 



