Chap. XXVII. OF PANGENESIS. 367 



generally from changed conditions acting during successive 

 generations. The fluctuating variability thus induced is ap- 

 parently due in part to the sexual system being easily affected, 

 so that it is often rendered impotent ; and when not so 

 seriously affected, it often fails in its proper function of 

 transmitting truly the characters of the parents to the 

 offspring. But variability is not necessarily connected with 

 the sexual system, as we see in the cases of bud- variation. 

 Although we are seldom able to trace the nature of the con- 

 nection, many deviations of structure no doubt result from 

 changed conditions acting directly on the organisation, in- 

 dependently of the reproductive system. In some instances 

 we may feel sure of this, when all, or nearly all the individuals 

 which have been similarly exposed are similarly and defi- 

 nitely affected, of which several instances have been given. 

 But it is by no means clear why the offspring should be 

 affected by the exposure of the parents to new conditions, 

 and why it is necessary in most cases that several generations 

 should have been thus exposed. 



How, again, can we explain the inherited effects of the use 

 or disuse of particular organs ? The domesticated duck flies 

 less and walks more than the wild duck, and its limb-bones 

 have become diminished and increased in a corresponding 

 manner in comparison with those of the wild duck. A 

 horse is trained to certain paces, and the colt inherits similar 

 consensual movements. The domesticated rabbit becomes 

 tame from close confinement; the dog, intelligent from 

 associating with man ; the retriever is taught to fetch and 

 carry ; and these mental endowments and bodily powers are 

 all inherited. Nothing in the whole circuit of physiology is 

 more wonderful. How can the use or disuse of a particular 

 limb or of the brain affect a small aggregate of reproductive 

 cells, seated in a distant part of the body, in such a manner 

 that the being developed from these cells inherits the charac- 

 ters of either one or both parents ? Even an imperfect answer 

 to this question would be satisfactory. 



In the chapters devoted to inheritance it was shown that a 

 multitude of newly-acquired characters, whether injurious or 

 beneficial, whether of the lowest or highest vital importance, 



