IX.] RETROGRESSIVE DEVELOPMENT IN NATURE. 5 



lessly, when pursued by the natives or by one of the few 

 indigenous birds of prey. It confines itself almost entirely to 

 the food it can find in the earth, especially worms, in searching 

 for which it is greatly assisted by the long beak with its delicate 

 sense of touch. It drives its bill into the soft damp ground, 

 much as the snipe does, and extracts the worms with great 

 skill and precision. 



When the species first arose, it was confined to the ground, 

 since nothing was to be gained ,by leaving it, and the physical 

 structure was therefore adapted to this mode of Hfe, by the 

 gradual elimination of the wings. If the species were only 

 now being formed, the above-mentioned change would most 

 probably not have occurred ; for with the invasion of its 

 domain by man, bringing his fire-arms and his cats and dogs, 

 the conditions of life of the Kiwi have been considerably 

 altered, and wings jnight now stand the helpless bird in good 

 stead. But they have been irretrievably lost, and the race of 

 Kiwis will consequently soon be extinct, hke the gigantic 

 ostrich-like birds, the Moas, which are known to have inhabited 

 New Zealand within the memory of man, and the skeletons of 

 which, over twelve feet high, arouse our wonder in museum 

 collections. 



As the winged ancestors of the Kiwi adapted themselves 

 more and more to life on the ground in the woods, they came 

 to use their wings less and less, and we may safely conclude 

 that this increasing tendency to disuse of the organs of flight, 

 continuing through long generations, affected the organs them- 

 selves, and in some indirect way diminished their size, gradually 

 reducing them to the insignificant appendages we now find. 



It is easy to understand how it is that degeneration has gone 

 further in the case of the Kiwi than in that of the ostrich ; for, 

 although the latter does not fly, it still uses its wings as aids in 

 running swiftly over the African plains and deserts, while 

 such rapid movement across open country is not necessary for 

 the Kiwi, living as it does in coverts. Short wings with large 

 feathers, like those of the ostrich, would be rather a hindrance 

 than otherwise to the Kiwi in moving quickly through thickets 

 and among underwood, and therefore its wings have been 

 reduced to mere rudiments which are externally altogether 

 invisible. 



