222 EVOLUTION OF TO-DA Y. 



change. As to what it may be that causes cer- 

 tain organs to be thus united we know nothing, but 

 that such correlated organs exist is beyond ques- 

 tion. It is not necessary, therefore, to assume that 

 all variations must be useful in order that they 

 be selected, but only that they are connected with 

 others which are useful. It may be that many of 

 these useless peculiarities are in this manner con- 

 nected with others that are useful, and that the de- 

 velopment of one implies the development of the 

 other. The useful variation will be preserved by 

 natural selection, and the useless variation will 

 necessarily be preserved and developed in a par- 

 allel manner. Much is attributed also to the 

 laws of growth, by which is meant the obscure 

 laws which regulate the flow of nutriment, etc. 

 Many important features may be thus explained. 

 Some plants have their leaves opposite each other, 

 others have them alternating ; and this point, of 

 no use to the plant, may be regulated by the flow of 

 sap in the two cases. But at best these two sugges- 

 tions are of little assistance, and simply serve to in- 

 dicate that there is an unexplained difficulty here. 

 That they do not sufficiently explain useless feat- 

 ures is so well proved that even Darwin was at last 

 inclined to admit the great potency of " spontaneous 

 variation," and with this phrase he abandons all at- 

 tempt to reach a clear understanding of the matter. 

 Natural selection thus fails to reach this large class 

 of features, which are of no use to their possessor, 

 and does not help in understanding the origin of 

 species whose distinctions are founded upon such 

 features. 



