SPECIES AS TO VARIATION ETC. 203 



taeine espece ? Parce qu'ils se ressemblcnt et uniquement a 

 cause de cela. Lorsque deux especes ne peuvent, ou, s'il s'agit 

 d'animaux superieurs, ne peuvent et ne veulent se croiser, c'est 

 qu'elles sont tres differentes. Si l'on obtient des croisements, 

 c'est que les individus sont analogues ; si ces croisements don- 

 nent des produits feconds, c'est que les individus etaient plus 

 analogues ; si ces produits eux-memes sont feconds, c'est que la 

 ressemblance etait plus grande ; s'ils sont fecond habituellement 

 et indefiniment, c'est que la ressemblance interieure et exterieure 

 £tait tres grande. Ainsi le degre de ressemblance est le fond ; 

 la reproduction en est seulement la manifestation et la mesure, 

 et il est logique de placer la cause au-dessus de l'effet." 



We are not yet convinced. We still hold that 

 genealogical connection, rather than mutual resem- 

 blance, is the fundamental thing — first on the ground 

 of fact, and then from the philosophy of the case. 

 Practically, no botanist can say what amount of dis- 

 similarity is compatible with unity of species ; in wild 

 plants it is sometimes very great, in cultivated races 

 often enormous. De Candolle himself informs us that 

 the different variations which the same oak-tree ex- 

 hibits are significant indications of a disposition to set 

 up separate varieties, which becoming hereditary may 

 constitute a race ; he evidently looks upon the extreme 

 forms, say of Quercus R6bui\ as having thus origi- 

 nated ; and on this ground, inferred from transitional 

 forms, and not from their mutual resemblance, he 

 includes them in that species. This will be more 

 apparent should the discovery of transitions, which 

 he leads us to expect, hereafter cause the four provi- 

 sional species which attend Q. Bohnr to be merged 

 in that species. It may rightly be replied that this 

 conclusion would be arrived at from the likeness step 



