346 [May 



SOME :n^ew books 



After Darwin 



Darwin and afteii Dakwin. By the late George John Romanes. Voh III. Post- 

 Darwinian Questions : Isolation and Physiological Selection. Cr. 8vo, pp. 181. 

 London: Longmans, Green & Co., 1897. Price, 10s. 6d. 



The third and last volume of " Darwin and after Darwin " deaLs en- 

 tirely with post-Darwinian questions, and is practically a re-statement 

 in rather clearer terms of the views of the autlior and others on isola- 

 tion and physiological selection. Clearness lias not hitherto been a 

 characteristic of the small school of writers represented by Eomanes 

 and Gulick, therefore a statement of their case in terms which could 

 be " understanded of the people " was really desirable. We cannot 

 think, however, that, having been so stated, it is likely to win over 

 more supporters from the ranks of the natural selectionists. The 

 more clearly the theory of physiological selection is formulated, the 

 less adequate it appears to produce the results claimed for it. It is a 

 very long way after Darwin indeed. That great master began with 

 facts, and only after years of patient accumulation of these did he think 

 himself justified in enunciating as general laws the conclusions he 

 drew from their study. 



Mr Eomanes' theory scarcely even pretends to be founded on 

 facts ; it is based on predictions which have as yet only received 

 even apparent verification in a very few cases, yet the author himself 

 admits that " the whole theory " must " stand or fall with the experi- 

 mental proof of the presence or the absence of cross-infertility be- 

 tween varieties of the same species growing on common areas." The 

 few facts he does adduce " as serving to corroborate " his theory are 

 scattered at wide intervals through the volume, and are drawn chiefly 

 from (1) a group of allied plants in one locality, and (2) "several 

 genera " of land mollusca. 



When we say that, on the authority of Le Conte, even the Stein- 

 heim snails {2Mce Weismann !) are requisitioned to add to this 

 category, it will be evident that the physiological selectionists have 

 not been able to produce an overwhelming amount of evidence from 

 direct observation. Meanwhile, cases " making directly against " the 

 theory are quietly dismissed in a note (p. 135) as "not numerous." 



The strength of the position taken up by natural selectionists lies 

 in the fact that their theory of the adequacy of natural selection to 

 produce divergence is based on the universally-admitted fact of indi- 

 vidual variability, and starts directly from this point ; they do not 

 claim anything more as material to work upon. All other theories 

 constantly require something to be taken for granted at the outset 

 which is not universally admitted. No argument, however closely 

 followed out to its logical conclusion, can be really convincing unless 

 it starts originally from undisputed facts ; the weak point of Eomanes' 

 book is that he is continually basing upon premisses which are, to say 



