Xll 



INTRODUCTION. 



illustration, Mr. Wallace reminds us that Madeira, like many other oceanic islands in the 

 temperate zone, is much exposed to sudden gusts of wind, and that, as most of the fertile 

 land is on the coast, insects which new much would be very liable to be blown out to sea 

 and lost. Year after year, therefore, those individuals which had shorter wings, or which 

 used them least, were preserved ; till in process of time, as we now see, the insects of 

 Madeira have become wingless and terrestrial, or, if they have not entirely lost their wings, 

 have had them so reduced as to be useless for flight. To my mind it would not be right to 

 confound these wingless insects with the lower forms of the " more generalised ancestors," 

 but rather to assign them a place among the "higher and more specialised groups." For it 

 must be borne in mind that, as Mr. Wallace himself expresses it (page 120), the "remarkable 

 advance in the higher and larger groups does not imply any universal law of progress in 

 organisation, because we have, at the same time, numerous examples of the persistence of 

 lowly-organised forms, and also of absolute degradation or degeneration. Serpents, for example, 

 have been developed from some lizard-like type which has lost its limbs ; and though this 

 loss has enabled them to occupy fresh places in nature, and to increase and flourish to a 

 marvellous extent, yet it must be considered to be a retrogression rather than an advance 

 in organisation. The same remark will apply to the Whale tribe among Mammals ; to the 

 blind amphibia and insects of the great caverns ; and among plants to the numerous cases 

 in which flowers, once specially adapted to be fertilised by insects, have lost their gay corollas 

 and their special adaptations, and have become degraded into wind-fertilised forms." But 

 it seems to me that on this point Mr. Wallace is inconsistent with himself ; because at 

 page 481, after referring to my figure of the wing in vol. iii. of our ' Transactions,' he says : 

 "Even in the Apteryx, the minute external wing bears a series of nearly twenty stiff quill- 

 like feathers " ; and he goes on to say, " These facts render it almost certain that the Struthious 

 birds do not owe their imperfect wings to a direct evolution from a reptilian type, but to 

 a retrograde development from some low form of winged birds, analogous to that which has 

 produced the Dodo and the Solitaire from the more pronounced Pigeon- type." He adds that 

 our best anatomists agree that both Dinornis and Apteryx are more nearly allied to the 

 Cassowaries and Emus than to the Ostriches and Bheas.* Now, from this point of view, 

 I think the language in which I long ago characterised the Kiwi— although challenged by 

 Professor Hutton and others— is fully justified, namely, that it is the diminutive and degenerate 

 representative of the ancient colossal forms of wingless birds. Its very existence, as we now 

 find it, is an illustration of the truth as formulated by Wallace himself, that " greater 

 swiftness, increased cunning, nocturnal habits, change of colour, or the power of climbing 

 trees and living for a time on their foliage or fruit, may be the means adopted by different 

 species to bring themselves into harmony with the new conditions; and by the continued 

 survival of those individuals only which varied sufficiently in the right direction, the necessary 

 modifications of structure or of function would be brought about, just as surely as man has 

 been able to breed the greyhound to hunt by sight and the foxhound by scent, or has 

 produced from the same wild plant such distinct forms as the cauliflower and the Brussels 

 sprouts, "f 



* At page 416, op. cit., Mr. Wallace says, " Whales, like Moas and Cassowaries, carry us back to a remote past, of 

 whose conditions we know too little for safe speculation. We are quite ignorant of the ancestral forms of either of these 

 groups, and are therefore without the materials needful for determining the steps by which the change took place, or the 

 causes which brought it about." 



+ Mr. Wallace, in acknowledging receipt of my pamphlet, wrote in appreciative terms of the paper as a whole, adding 

 that on the only points on which he disagreed with me he had communicated an article to Nature. On turning this up 

 (vol. Iii., p. 60) I found the following criticism : "Its main subject-matter is a discussion of the various ways in which 



