Chap. IV.] CONVERGENCE OP CHARACTER. 157 



forces, and it is not surprising that dissimilar substances 

 should sometimes assume the same form; but with or- 

 ganic beings we should bear in mind that the form of 

 each depends on an infinitude of complex relations, 

 namely on the variations which have arisen, these being 

 due to causes far too intricate to be followed out, — on 

 the nature of the variations which have been preserved 

 or selected, and this depends on the surrounding phys- 

 ical conditions, and in a still higher degree on the sur- 

 rounding organisms with which each being has come 

 into competition, — and lastly, on inheritance (in itself a 

 fluctuating element) from innumerable progenitors, all 

 of which have had their forms determined through 

 equally complex relations. It is incredible that the 

 descendants of two organisms, which had originally dif- 

 fered in a marked manner, should ever afterwards con- 

 verge so closely as to lead to a near approach to identity 

 throughout their whole organisation. If this had oc- 

 curred, we should meet with the same form, inde- 

 pendently of genetic connection, recurring in widely 

 separated geological formations; and the balance of evi- 

 dence is opposed to any such an admission. 



Mr. Watson has also objected that the continued 

 action of natural selection, together with divergence of 

 character, would tend to make an indefinite number of 

 specific forms. As far as mere inorganic conditions are 

 concerned, it seems probable that a sufficient number of 

 species would soon become adapted to all considerable 

 diversities of heat, moisture, &c.; but I fully admit that 

 the mutual relations of organic beings are more im- 

 portant; and as the number of species in any country 

 goes on increasing, the organic conditions of life must 

 become more and more complex. Consequently there 



