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Show 202 DARWINIAN A. equally have to be verified inferentially. !f we still hold to the idea of Linnreus, and of Agassiz, that ex. t' 'es were created independently and essenIS mg spem tially all at once at the beginni~~ of the ~resent era, we could not better the propositions of .Lmmeus and f J · If on the other band, the time has come 0 USSieU. ' . in which we may accept, with De Oandolle, thmr sue-cess. i ve ori·g 1· nati'on ' at the commenc.e me. nt of the pres-en t era oi. before, and even by denv.a twn from. other f th n the " in principio " of Linnreus will refer orms, e h' . . b to that time, whenever it was, and IS proposition e as sound and wise as ever. · In his" Geographie Botanique" (ii., 1068-10!7) De Oandolle discusses this subject at length, and m the 'nterest. Remarking that of the two great facts same I • . 'd l d of s eci.es, viz., likeness among tl~e ~nd~v~ ua s, an gene;logical connection, zoologists have gene:·~l1y pr.eferred the latter/ while botanists have been divided m op·m w· n, he pronounces for the forme.r as the essen- · tial thing, in the fo1lowing argumentative statement: " Quant a moi j'ai ete conduit, dans ma definition de l'espece, a mettre decidem~nt la ressemblance au-dessus de c~racteres de successi·O n. 0 e n'est pas seulement a cause des c.u constances :.gne vt.gt.tal dont J·e m'occupe exclus1veroent; ce propres au rtJ tJ tJ ' · d n'est pas non plus afin de sortir ma definiti?n des the?nes et e la rendre le plus possible utile aux natu~ahstes .descnpteurs et nomenclateurs c'est aussi par un motif phllosopblque. En toute chose il faut aller au fond des questions, quand on le peut. Or, pourquoi la reproduction est-elle possible, habituel~e, feconde indefiniment, entre des Mres organises que nous dirons de la 1 Particularly citing Flourens: "La ressemblance n'est qu'une condition secondaire; la condition essentielle e~t 1~ ~escend~:ri~e \ ce ~':s,! pas la ressemblance, c'est la succession des mdlVldus, qm falt l espec • SPECIES AS TO VARIATION, ETC. 203 m~me espece? Parce qu'ils se ressemblent et uniquement a cause de cela. Lorsque deux esp(wes ne penvent, on, s'il s'agit d'animaux superieurs, ne peuvent et ne veulent se croiser, c'ost qu'elles sont tres differentes. Si l'on obtient des croisements c'est que les individus sont analogues; si ces croisements don~ nent dos produits feconds, c'est que les individus etaient plus analogues; si ces produits eux-m~mes 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 etait 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 resemblance, 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 dissimilarity is compatible with unity of species ; in wild plants it is sometimes very great, in cultivated races often enormous. De Oandolle himself informs us that the different variations which the same oak-tree exhibits are significant indications of a disposition to set up separate varieties, ~hich becoming hereditary may constitute a race; he evidently looks upon the extreme· forms, say of Quercus Robur, as having thus originated; and on this ground, inferred from transitional forms, and not from their mutual resemblance he includes them in that species. This will be ~ore apparent should the discovery of transitions, which he leads us to expect, hereafter cause the four provi~ ional specie~ which attend Q. Robur to be merged m that species. It may rightly be replied that this conclusion would be arrived at from the likeness step |
