170 MISCELLANEOUS OBJECTIONS TO THE [Chap. VII 



hi single characters, but in many parts ; and he asks, how it always 

 comes that many parts of the organisation should have been modi- 

 fied 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 successive variations, if slight, 

 first in one part and then in another ; and as they would be trans- 

 mitted all together, they would appear to us as if they had been 

 simultaneously 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 selection, 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 

 invariably 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 characters appear to be of no 

 service whatever to their possessors, and therefore cannot have been 

 influenced through natural selection. Bronn adduces the length of 

 the ears and tails in the different species of hares and mice, — the 

 complex folds of enamel in the teeth of many animals, and a 

 multitude of analogous cases. With respect to plants, this subject 

 has been discussed by Nageli in an admirable essay. He admits that 

 natural selection has effected much, but he insists that the families 

 of plants differ chiefly from each other in morphological characters, 

 which appear to be quite unimportant for the welfare of the species. 

 He consequently believes in an innate tendency towards progressive 

 and more perfect development. He specifies the arrangement of the 

 cells in the tissues, and of the leaves on the axis, as cases in which 

 natural selection, could not have acted. To these may be added 

 the numerical divisions in the parts of the flower, the position 

 of the ovules, the shape of the seed, when not of any usie for dis- 

 semination, &c. 



