158 NATURAL SELECTION vn 



curious modifications of plumage, and the capacity of per- 

 petual egg-laying. In pigeons we have a still more remark- 

 able proof of the universality of variation, for it has been at 

 one time or another the fancy of breeders to change the form 

 of every part of these birds, and they have never found the 

 required variations absent. The form, size, and shape of bill 

 and feet have been changed to such a degree as is found only 

 in distinct genera of wild birds ; the number of tail feathers 

 has been increased, a character which is generally one of the 

 most permanent nature, and is of high importance in the 

 classification of birds ; and the size, the colour, and the habits 

 have been also changed to a marvellous extent. In dogs, 

 the degree of modification and the facility with which it is 

 effected is almost equally apparent. Look at the constant 

 amount of variation in opposite directions that must have 

 been going on to develop the poodle and the greyhound from 

 the same original stock ! Instincts, habits, intelligence, size, 

 speed, form, and colour have always varied, so as to produce 

 the very races which the wants or fancies or passions of 

 men may have led them to desire. Whether they wanted a 

 bull-dog to torture another animal, a greyhound to catch a 

 hare, or a bloodhound to hunt down their oppressed fellow- 

 creatures, the required variations have always appeared. 



Now this great mass of facts, of which a mere sketch has 

 been here given, are fully accounted for by the "Law of 

 Variation " as laid down at the commencement of this paper. 

 Universal variability small in amount, but in every direction, 

 ever fluctuating about a mean condition until made to advance 

 in a given direction by " selection," natural or artificial is 

 the simple basis for the indefinite modification of the forms 

 of life ; partial, unbalanced, and consequently unstable modi- 

 fications being produced by man, while those developed under 

 the unrestrained action of natural laws are at every step self- 

 adjusted to external conditions by the dying out of all 

 unadjusted forms, and are therefore stable and comparatively 

 permanent. 1 To be consistent in their views, our opponents 

 must maintain that every one of the variations that have 

 rendered possible the changes produced by man have been 



1 That the variations occiirring among wild animals are ample both in num- 

 ber and amount is proved in Darvrinism, chap. iii. 



