NATURAL SELECTION 93 



the young should be helpless, since, if so, they cannot stray or 

 get lost while their parents are collecting supplies. 



In the examples chosen the process is clear enough. The con- 

 ditions have changed, and characters that were formerly useful 

 have become injurious. Natural Selection, therefore, accounts 

 for their disappearance without difficulty. 



We now pass on to our second case, where the principle of 0) to 



r . ,1 i . economy 



economy of growth may be called in. of growth 



The apteryx or kiwi now possesses mere vestiges of wings, 

 but there is no doubt that he is descended from progenitors in 

 which the fore-limb was fully developed. He is a ground- 

 feeder, and as there are in his habitat, New Zealand, no mam- 

 mals save bats and rats, nor any formidable reptiles, flight 

 would be a useless accomplishment. But it does not follow 

 that it would involve danger. The habits of the kiwi being 

 what they are, and New Zealand broad and spacious, there 

 would be little danger that storms would carry him out to sea. 

 Thus, whether the kiwis once possessed the power of flight or 

 not, it can hardly be said that the possession of fully-developed 

 fore-limbs would bring any peril with it. Yet their maintenance 

 might cause a reduced flow of nutriment to other parts of the 

 body, where it was much needed. 



In the vegetable kingdom, too, there are plenty of examples 

 of the loss of organs, which may have been injurious because of 

 the cost of their maintenance. There is good reason to believe 

 that the grasses are degenerate lilies. In their present state they 

 are wind-fertilised. They have no calyx or corolla ; they pro- 

 duce no honey, and are not visited by insects. But the two tiny 

 scales, called lodicules, are, according to the accepted theory, 

 vestiges of a perianth. If so, and there is good reason for hold- 

 ing this view, the grasses once had showy flowers for attracting 

 insects ; but, since many plants of a species often clustered to- 

 gether, the wind proved a better fertiliser, and the perianth dis- 

 appeared. A stop, we may hold, was put to wasteful expenditure. 

 But before accepting this view, we must clearly define what 

 is meant by wasteful expenditure, since it is not so clear what 

 constitutes waste when we are speaking of a species and not an 



