Chap. XXVII. OF PANGENESIS. 371 



each of which possesses its own proper attributes, and is to a 

 certain extent independent of all others. Hence it will be con- 

 venient to use indifferently the terms cells or organic units or 

 simply units. 



Variability and Inheritance.— We have seen in the twenty- 

 second chapter that variability is not a principle co-ordinate 

 with life or reproduction, but results from special causes 

 generally from changed conditions acting durino- successive 

 generations. Part of the fluctuating variability thus induced 

 is apparently due to the sexual system being easily affected 

 by changed conditions, 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 from the cases of bud-variation ; 

 and although we may not be able to trace the nature of the 

 connexion, it is probable that many deviations of structure which 

 appear in sexual offspring result from changed conditions acting 

 directly on the organisation, independently of the reproductive 

 organs. In some instances we may feel sure of this, when all, or 

 nearly all the individuals which have been similarly exposed are 

 similarly and definitely affected— as in the dwarfed and otherwise 

 changed maize brought from hot countries when cultivated in 

 Germany ; in the change of the fleece in sheep within the tropics ; 

 to a certain extent in the increased size and early maturity of 

 our highly-improved domesticated animals ; in inherited gout 

 from intemperance ; and in many other such cases. Now, as 

 such changed conditions do not especially affect the reproductive 

 organs, it seems mysterious on any ordinary view why their 

 product, the new organic being, should be similarly affected. 



How, again, can we explain to ourselves 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 in a corresponding manner diminished 

 and increased m 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 



2 b 2 



