On the Mechanical Conception of Nature. 701 



naturalists this should be once and for ever 

 abandoned. 



All other facts which have hitherto been 

 referred to " heterogeneous generation " are still 

 less explicable as such, inasmuch as they always 

 relate to changes in single parts of an organism, 

 such as the sudden change of fruit or flower in 

 cultivated plants. The notion of per saltum de- 

 velopment, however, demands a total transfor- 

 mation it comprises (as Von Hartmann quite 

 correctly and logically admits) the idea of a fixed 

 specific type which can only be re-modelled as a 

 whole, and cannot become modified piecemeal. 

 It must further be added, that the observed 

 variations which have arisen abruptly in single 

 parts are not as a rule inherited: 4 fruit-trees are 

 only propagated by grafting, i.e. by perpetuating 

 the individual, and not by ordinary reproduction 

 by seeds. Now, if we nowhere see sudden varia- 

 tions of large amount perpetuated by heredity, 

 whilst we everywhere observe small variations 

 which can all be inherited, must it not be con- 

 cluded that per saltum modification is not the 

 means which Nature employs in transforming 

 species, but that an accumulation of small varia- 

 tions takes place, these leading in time to large 

 differences? Is it logical to reject the latter con- 

 clusion because our period of observation is too 



4 [See Darwin's "Origin of Species," 6th ed. pp. 33, 34, and 

 201 204. R. M.] 



Z z 2 



