Buller. — Illustrations of Darwinism. 85 



direction, and in the southern part in another direction ; and, 

 though for a long time an intermediate form may continue to 

 exist in the intervening area, this will be likely soon to die out, 

 both because its numbers will be small, and it will be more or 

 less pressed upon in varying seasons by the modified varieties, 

 each better able to endure extremes of climate. So, when one 

 portion of a terrestrial species takes to a more arboreal or to a 

 more aquatic mode of life, the change of habit itself leads to 

 the isolation of each portion." 



Now, it is not difficult to imagine that in the case of a 

 country which was gradually emerging from the depths of the 

 ocean, presenting for long-continued periods of time low flats 

 more or less covered with scrubby vegetation, available for 

 purposes of concealment, a smaller size would be beneficial to 

 the already practically wingless birds, the more so if correlated 

 with a longer bill, for the purpose of hunting for annelids 

 and insects in the increasing deposits of mould covering 

 these newly-formed flats. And, bearing in mind that natural 

 selection acts solely "by the preservatiota of useful varia- 

 tions, or those which are beneficial to the organism under 

 the conditions to which it is exposed," we should in this 

 case regard the so-called degeneration of the Kiwi as an im- 

 provement in the organism of the bird in relation to its 

 conditions and environment. So also, in regard to those 

 wingless birds which continued to inhabit the table-lands, and 

 to subsist on fern-roots and the ever-present " cabbage-tree," 

 should we regard a longer neck and a stronger bill as beneficial 

 variations, especially if correlated with a more massive pos- 

 terior development, such as that which distinguishes Dinornis 

 elephantopus and Dinornis crassus. May not the giant Kiwi 

 (Megalaptcryx hectori), the remains of which were discovered 

 and described by the late Sir Julius von Haast, represent one 

 of the intermediate forms which have been stamped out and 

 lost in the long-continued struggle for existence along the 

 borderland, so to speak, of these different races of wingless 

 birds? 



As I have already stated, each so-called species of Kiwi is 

 restricted in its range to a particular district. In the case of 

 Apteryx mantelli and Apteryx laicryi this is insular, save as to 

 the appearance of the Grey Kiwi on the Tararua Eange, which 

 I shall presently endeavour to account for. Now, if any 

 sudden catastrophe were to overtake New Zealand, destroying 

 all animal life, the remains of the different species of Kiwi 

 (so far as they could be distinguished) would be found in dif- 

 ferent localities and never commingled. This is not the case 

 with Dinornis and its allies. The bones of about a thousand 

 birds were exhumed by Sir Julius von Haast from the Glen- 

 mark marshes, and these comprised the skeletous of several 



