EVIDENCES FROM MORPHOLOGY 



U3 



quently we can understand why on this island we should meet with 

 such a remarkable dwindling away of wings. 



Similarly, the logger-headed duck of South America can only flap 

 along the surface of the water, having its wings considerably reduced 

 though less so than the Apteryx of New Zealand. But here the 

 interesting fact is that the young birds are able to fly perfectly well. 

 Now, in accordance with a general law to be considered in a future 

 chapter, the life-history of an individual organism is a kind of con- 

 densed recapitulation of the life-history of its species. Consequently, 

 we can understand why the little chickens of the logger-headed duck 

 are able to fly like all other ducks, while their parents are only able 

 to flap along the surface of the water. 



Facts analogous to this reduction of wings in birds which have no 

 further use for them, are to be met with also in insects under similar 

 circumstances. Thus, there are on the island of Madeira somewhere 

 between 500 and 600 species of beetles, which are in large part peculiar 

 to that island, though related to other — and therefore presumably 

 parent — species on the neighboring continent. Now, no less than 200 

 species — or nearly half the whole number — are so far deficient in 

 wings that they cannot fly. And, if we disregard the species which 

 are not peculiar to the island — that is to say, all the species which 

 likewise occur on the neighboring continent, and therefore, as evolu- 

 tionists conclude, have but recently migrated to the island, — we find 

 this very remarkable proportion. There are altogether 29 peculiar 

 genera, and out of these no less than 2t, have all their species in this 

 condition. 



Similar facts have been recently observed by the Rev. A. E. Eaton 

 with respect to insects inhabiting Kerguelen Island. All the species 

 which he found on the island — viz., a moth, several flies, and numerous 

 beetles — he found to be incapable of flight; and therefore, as Wallace 

 observes, "as these insects could hardly have reached the islands in 

 a wingless state, even if there were any other known land inhabited 

 by them, which there is not, we must assume that, like the Madeiran 

 insects, they were originally winged, and lost their power of flight 

 because its possession was injurious to them" — Kerguelen Island 

 being " one of the stormiest places on the globe, " and therefore a place 

 where insects could rarely afford to fly without incurring the danger 

 of being blown out to sea. 



Here is another and perhaps an even more suggestive class of 

 facts. 



