I 



1894. 7^^^ ORIGIN OF SPECIES. 261 



If the rocky environment is to be credited with species-making in the 

 one case, so must Kew be in the other. In both cases there is neither 

 mention made nor need of any selection at all. Mr. Elwes told me 

 that the various bulbous plants he introduced from the East into his 

 garden at Preston, Cirencester, changed so greatly in a few years in 

 all their parts that he could scarcely recognise them again. 



Mr. Wallace adds : " Other forms, with no greater peculiarities 

 externally, preserve their characters under cultivation, though 

 exposed to the most varied conditions." 



This is equally and quite true ; but any investigation into the 

 causes of the. origin of species by variation has nothing to do with any 

 other question of the causes of preservation of the type-characters, or 

 heredity. Evolution accounts for all living beings by variation ; but it 

 does not attempt to offer any explanation of the existence of 

 " survivals." E.g., Nautilus and Lingula have lived on from the 

 Silurian days till now ; Equisetum has flourished from, at least, the 

 Carboniferous epoch till to-day. Therefore change is not absolutely 

 necessary in organisms under changed conditions ; but when it does occur, 

 then I maintain, with Dr. Weismann, that all changes are primarily 

 due to external influences. He says : " We are driven to the con- 

 clusion that the ultimate origin of hereditary individual differences 

 lies in the direct action of external influences upon the organism. "9 



Mr. Wallace is good enough to call attention to my book, " The 

 Origin of Floral Structures by Insect and Other Agencies," ^° and, 

 attacks, very rightly, what I fully admit may be regarded as a weak 

 point in it ; i.e., I can bring but few positive illustrations to demon- 

 strate my view that irregular flowers have been formed through the 

 direct action of insects from regular ones ; but he quite ignores the 

 whole line of argument running through the book in support of the 

 probability. It is one which Dr. Weismann recommends in support 

 of evolution, which " may be maintained with the same degree of 

 certainty as that with which astronomy asserts that the earth moves 

 round the sun ; for a conclusion may be arrived at as safely by other 

 methods as by mathematical calculation."" It is the well known 

 argument of the accumulation of coincidences which can furnish 

 probabilities of so high an order that they may be regarded as an 

 equivalent to a demonstration. Thus, physicists tell us that they 

 knoiv the composition of the sun, but their knowledge is solely based 

 on the coincidences between the lines of the solar spectrum and those 

 of vapourised substances. '^ Similarly with flowers : when we find 

 innumerable coincidences all tending in one direction, coupled with 

 an indefinite capacity for varying in response to forces in all parts of 



^ " Essays on Heredity," etc. Eng. trans., p. 279. 

 10 International Scientific Series, vol. Ixiv. 

 " " Essays on Heredity," etc., p. 255. 



1- The " fact" that udders have become enlarged by hand-milking is based on a 

 similar accumulation of probabilities. 



