VIII DARWINISM AND HOLISM 207 



vidual in whom it appears. It is protected, shielded and 

 in its struggle reinforced, by this constant use and routine. 

 A small variation in the direction of a nascent organ, for 

 instance, finds itself in line with the traditional use of 

 generations of individuals which powerfully support it in 

 the struggle with contrary variations. Under the shelter of 

 this use it develops and beats its competitors, until in the 

 end it can fend for itself and engage in the struggle on its 

 own account. 



This explanation applies not only to variations in develop- 

 ing organs which are supported by use and practice on the 

 part of a long line of individuals. It applies also to cases 

 where permanent changes in the physical conditions impress 

 themselves continuously on the organism. The growth 

 forms of plants, for instance, under particular ecological 

 conditions are such as almost to render necessary the view 

 that ecological modifications, due to the direct, silent, long- 

 continued pressure of the environment, finally become varia- 

 tions. The sameness or close resemblance of the growth 

 forms under the same physical conditions, as seen, for in- 

 stance, in the general characters of formations and associa- 

 tions in the vegetable kingdom, are probably in a measure 

 due to the age-long operation of ecological factors which 

 have impressed themselves on plant development and have 

 produced modifications which finally have become varia- 

 tions.^ The resulting general features of formations and 



* While this book was going through the press I was much inter- 

 ested to see this view corroborated by certain observations of Professor 

 F. O. Bower in Evolution in the Light of Modern Knowledge (p. 206). 

 After discussing the evolutionary structures of ferns he continues: "It 

 would seem a natural interpretation of the facts that the characters 

 (under discussion), acquired by a direct impress upon a succession 

 of individual lives, should have been imposed hereditarily upon 

 each race. Naturally the reply may be made that probably muta- 

 tions favourable to the perpetuation of the imposed character may 

 have made that character permanent. If we grant that, do 

 we not thereby simply admit that the distinction between fluctuat- 

 ing variations and mutations is not absolute? In other words, that 

 fluctuating variations repeatedly imposed upon successive generations are 

 liable to become mutations? It is difficult to see any other rational 

 explanation of the wide-reaching facts of homoplastic adaptation, such 

 as are shown with exceptional profusion in the ancient class of the ferns, 

 and are evident in plants at large." (In this quotation fluctuating 



