IV.] MINUTE MODIFICATIONS. 115 



second generation, reverted to the original types, as true 

 hybrids do." l 



There are, then, abundant instances to prove that con- 

 siderable modifications may suddenly develop themselves, 

 either due to external conditions or to obscure internal 

 causes in the organisms which exhibit them. Moreover, 

 these modifications, from whatever cause arising, are 

 capable of reproduction the modified individuals "breed- 

 ing true." 



The question is whether new species have been de- 

 veloped by non- fortuitous variations which are insignifi- 

 cant and minute, or whether such variations have been 

 comparatively sudden and of appreciable size and im- 

 portance ? Either hypothesis will suit the views here 

 maintained equally well (those views being opposed only 

 to fortuitous indefinite variations), but the latter is the 

 more remote from the Darwinian conception, and yet has 

 much to be said in its favour. 



Professor Owen considers, with regard to specific origina- 

 tion, that natural history " teaches that the change would 

 be sudden and considerable : it opposes the idea that 

 species are transmitted by minute and slow degrees." 2 

 " An innate tendency to deviate from parental type, 

 operating through periods of adequate duration," being 



1 In confirmation of the suddenness of occasional changes, a remark 

 recently made by Mr. Darwin should be quoted. He says : "It is also 

 well to reflect on such facts as the wonderful growth of galls on plants 

 caused by the poison of an insect, and on the remarkable changes of colour 

 in the plumage of parrots when fed on certain fishes, or inoculated with 

 the poison of toads ; for we can thus see. that the fluids of the system, if 

 altered for some special purpose, might induce other strange changes." 

 Descent of Man, vol. i. p. 152. 



2 "Anatomy of Vertebrates, " vol. iii. p. 795. 



I 2 



