LAWS OF VARIATION 129 



another ; for it is not likely that man should have suc- 

 ceeded in selecting so many breeds and sub-breeds with 

 constitutions specially fitted for their own districts : 

 the result must, I think, be due to habit. On the other 

 hand, I can see no reason to doubt that natural selection 

 will continually tend to preserve those individuals which 

 are born with constitutions best adapted to their native 

 countries. In treatises on many kinds of cultivated 

 plants, certain varieties are said to withstand certain 

 climates better than others : this is very strikingly 

 shown in works on fruit trees published in the United 

 States, in which certain varieties are habitually recom- 

 mended for the northern, and others for the southern 

 States ; and as most of these varieties are of recent 

 origin, they cannot owe their constitutional differences 

 to habit. The case of the Jerusalem artichoke, which 

 is never propagated by seed, and of which consequently 

 new varieties have not been produced, has even been 

 advanced — for it is now as tender as ever it was — as 

 proving that acclimatisation cannot be effected ! The 

 case, also, of the kidney-bean has been often cited for a 

 similar purpose, and with much greater weight ; but 

 until some one will sow, during a score of generations, 

 his kidney-beans so early that a very large proportion 

 are destroyed by frost, and then collect seed from the 

 few survivors, with care to prevent accidental crosses, 

 and then again get seed from these seedlings, with the 

 same precautions, the experiment cannot be said to 

 have been even tried. Nor let it be supposed that no 

 differences in the constitution of seedling kidney-beans 

 ever appear, for an account has been published how 

 much more hardy some seedlings appeared to be than 

 others. 



On the whole, I think we may conclude that habit, 

 use, and disuse, have, in some cases, played a consider- 

 able part in the modification of the constitution, and 

 of the structure of various organs ; but that the effects 

 of use and disuse have often been largely combined 

 with, and sometimes overmastered by the natural 

 selection of innate variations. 



