366 Professor W. H. Flower on the Wings of Birds. [Feb. 19, 



to those described above. The structure of the wing separates the 

 penguins sharply from all the other carinate birds. 



The Ratitae, or birds without keel to the sternum, form another very- 

 distinct group, distinguished by the rudimentary or imperfect con- 

 dition of the remiges or quills, which never have coherent barbs and 

 are therefore unfitted to the purpose of flight. In the ostrich and 

 rhea the bones, though comparatively small, are distinct and complete, 

 and the feathers large and definitely arranged. The emu, cassowary, 

 and apteryx show various degrees of degeneration, which apparently 

 culminated in the dinornis, no trace of a wing-bone of which bird 

 has ever been found. The question which naturally presents itself 

 with regard to these birds is, whether they represent a stage through 

 which all have j)assed before acquiring perfect wings, or whether 

 they are descendants of birds which had once such wings, but which 

 have become degraded by w^ant of use. In the absence of palteonto- 

 logical evidence it is difficult to decide this point. The complete 

 structure of the bony framework of the ostrich's wing, with its two 

 distinct claws, rather points to its direct descent from the reptilian 

 hand, without ever having passed through the stage of a flying organ. 

 The function of locomotion being entirely performed by powerfully 

 developed hind-legs, and the beak mounted on the long flexible neck 

 being sufficient for the offices commonly performed by hands, the 

 fore-limbs appear to have degenerated or disappeared, just as the 

 hind-limbs of the whales disappeared when their locomotory functions 

 were transferred to the tail. This view is strengthened by the great 

 light that has been thrown on the origin of the wings of the flying 

 birds by the fortunate discovery of the Arcliseopteryx of the Solenhofen 

 beds of Jurassic age, as in this most remarkable animal, half lizard and 

 half bird, the process of modification from hand to perfect flying bird is 

 clearly demonstrated. The three digits which in the existing forms 

 are more or less pressed together and imperfect, still retain their free- 

 dom and complete number of phalanges, and are each armed with 

 terminal claws, while the flight feathers and remiges of the cubital, 

 metacarpal, and digital series are fully developed and evidently 

 functional. The earlier stages in which the outer digits were still 

 present, and the feathers imperfectly formed or merely altered scales, 

 are not yet in evidence. 



Some conception of the process by wliich a wing may have been 

 formed may also be derived from the study of the growth of feathers 

 on the feet* of some domestic varieties of pigeons and poultry, illustra- 

 tions of which were shown at the lecture. 



[W. H. F.] 



