PARTICULAR CASES 211 



It must also be remembered that Weismann expressly admits 

 that climatic influences, especially if long-continued, may influ- 

 ence the germ-plasm along with the whole system, and may induce 

 germinal variations that come to stay ; but this " has certainly 

 nothing to do with the view that functional modifications of any 

 particular organ can cause a corresponding change in the 

 germ-plasm." (See The Germ-Plasm, 1893, p. 408.) 



In adjacent areas with different climatic and other environ- 

 mental conditions we not infrequently find closely related 

 species or local races. It seems impossible to doubt that these 

 are blood-relations, derived from a common ancestor. Are 

 thej' not due to the environmental differences ? In some way, 

 surely, the organismal differences are causally correlated with the 

 environmental differences, and it is granted by all that pecu- 

 liarities of climate induce changes in the nutrition, respiration, 

 circulation, and so on. If so, the germ-plasm may be affected 

 and variations may be provoked, some of which are adaptive. 

 But the result of these variations may be something different 

 from and much more profitable than the modifications directly 

 induced. They may be expressed in relation to quite different 

 organs. Thus it seems quite unnecessary to believe in the trans- 

 mission of climatic modifications as such, or in any representa- 

 tive degree. Moreover, we must never forget that the active 

 organism must be credited with the power of seeking out en- 

 vironments which suit its inborn nature — variations included. 



Plants in New Environment.— Much has been made of the 

 changes which follow a radical change of environment. When 

 a plant is transferred to a new soil and climate it may undergo 

 a very marked change of habit ; its leaves may become hairy, 

 its stem woody, its branches drooping. " These," Herbert 

 Spencer said, " are modifications of structure consequent on 

 modifications of function that have been produced by modifica- 

 tions in the actions of external forces. And as these modifications 

 reappear in succeeding generations, we have, in them, examples 



