OBJECTIONS TO THE THEORY 291 



and he asks, how it always comes that many parts of the 

 organization should have been modified at the same time 

 through variation and natural selection ? But there is no 

 necessity for supposing that all the parts of any being 

 have been simultaneously modified. The most striking 

 modifications, excellently adapted for some purpose, 

 might, as was formerly remarked, be acquired by suc- 

 cessive variations, if slight, first in one part and then in 

 another; and as they would be transmitted all together, 

 they would appear to us as if they had been simulta- 

 neously developed. The best answer, however, to the 

 above objection is afforded by those domestic races which 

 have been modified, chiefly through man's power of se- 

 lection, for some special purpose. Look at the race and 

 dray horse, or at the greyhound and mastiff. Their 

 whole frames and even their mental characteristics have 

 been modified; but if we could trace each step in the 

 history of their transformation — and the latter steps can 

 be traced — we should not see great and simultaneous 

 changes, but first one part and then another slightly 

 modified and improved. Even when selection has been 

 applied by man to some one character alone — of which 

 our cultivated plants offer the best instances — it will in- 

 variably be found that although this one part, whether 

 it be the flower, fruit, or leaves, has been greatly 

 changed, almost all the other parts have been slightly 

 modified. This may be attributed partly to the principle 

 of correlated growth, and partly to so-called spontaneous 

 variation. 



A much more serious objection has been urged by 

 Bronn, and recently by Broca, namely, that many char- 

 acters appear to be of no service whatever to their 



