Botany and Zoology. 



289 



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observed) it does absolutely appear, that those species, the external 

 aspects of which have been thus artificially controlled, are by constitu- 

 tion more tractile (and possess, therefore, more decided powers for aber- 

 ration,) than the rest. Whether traces of design may be recognized in 

 this circumstance, or whether those forms were originally selected by 

 man on account of their pliability, it is not for me to conjecture ; never- 

 theless, the first of these inferences is the one which I should, myself, 

 be a priori inclined to subscribe to. 



In examining, however, this enigma, of the limits within which varia- 

 tion is (as such) to be recognized, it should never be forgotten, that it is 

 possible for those boundaries to be absolutely and critically marked out 

 even where we are not able to discern them : so that the difficulty which 

 a few domesticated creatures of a singularly flexible organization present, 

 should not unnecessarily predispose us to dispute the question in its 

 larger and more general bearings. Nor should we be unmindful that 

 (as Sir Charles Lyell has aptly suggested) " some mere varieties present 

 greater differences, inter se, than do many individuals of distinct specks ;" 

 for it is a truth of considerable importance, and one which may help us 

 out of many an apparent dilemma. 



But, whatever be the several ranges within which the members of the 

 organic creation are free to vary, we are positively certain that, unless 

 the definition of a species, as involving relationship, be more than a delu- 

 sion or romance, their circumferences are of necessity real, and must be 

 indicated somewhere, — as strictly, moreover, and rigidly, as it is possible 

 for anything in Nature to be chalked out. The whole problem, in that 

 case, does in effect resolve itself into this, — Where, and how, are the lines 

 of demarcation to be drawn ? No amount of inconstancy, provided its 

 limits be fixed, is irreconcilable with the doctrine of specific similitudes. 

 Like the ever-shifting curves which the white foam of the untiring tide 

 describes upon the shore, races may ebb and flow ; but they have their 

 boundaries, in either direction, beyond which they can never pass. And 

 thus in every species we may detect, to a greater or less extent, the em- 

 blem of instability and permanence combined : although perceived, 

 when inquired into, to be fickle and fluctuating in their component 

 parts, in their general outline they remain steadfast and unaltered, as of 

 old,— 



" Still changing, yet unchanged ; still doom'd to feel 

 Endless mutation, in perpetual rest." 



5. On the Fi*esh water Entomostraca of South America ; by John 

 Lubbock, Esq., F.Z.S., (Trans. Ent. 8vo, iii, N. S., Part vi ) -Mr. Lubbock 

 who has taken up the investigation of the Entomostraca with great 

 zeal and success, describes in this paper four new species of Entomostraca 

 from South America, Cypris australis, C. brasiliensis, Daphnia bra- 

 siliensis, and Diaptomus brasiliensis. They were collected by Charles 

 Darwin, Esq. 



SECOND SERIES, VOL. XXII, NO. 65. SEPT., 1856. 



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