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Show 260 EXPLANATIONS. subject-" According to some botanists, Afgre of a very simple structure, placed under favorable cucumst~nccs, develop and change into different plants, bel~ngin~ to genera much more elevated .in the scale of or9an1c being, although these same algre, In .th~ absence of su:h favc:able circumstances would be fertile, and reproduce their primitive form.''* ' I wou}d ask .if. this is a point as y~t settled in the negati v~.. fhe o~Iginal of our. cabba~~ 1s well known to be a trailing sea-side plant, entirely different from the cabbage in appearance. The cardoon a~d artichoke are now admitted to be one, and Mr. Dar~1n was assured by an intelligent farmer t~at ~e has seen, In a deserted garden, the latter plant relapsmg 1nto the former. It is well known that when fresh-water mollusks are exposed for a little time to an influx of. the sea, ~h?se which can survive the change assum~ constdera?ly dtfferent characters. In a fresh-water tertiary format1_on of the island of Cos, Professor Edward F0rbes and Lteutenant Spratt found various fresh-~:vater mollusc_an shclls-paludina, neretina, mclanopsis,. &c :--which had passed through sut'prising modifica!1ons 1n the course of three successive groups of deposits, supposed to have been marked by increasing influxes of sea-water. "The lowermost specie~ of each genus were smooth, those of~ the centre partially plicate~, and those _of the upper part strongly and regularly nbbed. "t Tlus ~as ap?ar~ntly a retro<rres')ion to manne tj"!"pCS. The dlff~rences In ~he three.., cases were greater than th~se "':hi_ch _naturah::;ts usually consider as grounds of specific d1shnchon .. Surely there are here ample evidences of species, or what are usually regarded ~s such, ~eing variable und:r chana-eel conditions. It w 11l be sa1d, these changes aie all m~re variations of specific forms, and the .facts ~o n~thing but show that that ha~ bee.n called sp~c1e~ ~ h .. I~h IS only variety. But where IS this to have Its hmits · If the cabba~e and sea-plant are to be now regarde9 as on~ speci , it seems to m.e that we have. to go very ~1ttl.~ f~I· ther to come to the hnes of succcss1:ve forms 01 stzrpt.fl, which nty hypothesis suggests. 'flus v1ew bec_o~es. the more stri kin(T when we remember that any "auat1_cns which we n~w see take place within a space of time • CharlPsvmrth's Magazine of Natural. J:Iistory, ii.! 4~ft 845 _ t Report of the Proceedings of the Dntlsh Assocuth{\n, 1 L.tc1"a·ry Gazelle. !IV A THERIU.M AND GIRAITE. M1 extremely small in comparison with those whit h geology allows for it phenomena. "Although,'' says Mr. Hal .. deman, "we may not be able, artificially, to produce a change beyond a definite point, it would be a hasty inference to suppose that a physical agent acting gradually for ages, could not carry tlie variation a step or two further." I may here advert to a fallacy which has been one of the principal difficulties in the way of the supposition of every kind of transmutation. It is always taken for granted that the parental animal must be extinguished in consequence of the change. Thus we find a suggestion by M. St. Hilaire that the modern giraffe may be a modjfi. cation of the sivatherium of the Indian tertiaries, met very. complacently by a reference to the discovery of Dr. Falconer, that in these tertiaries, the giraffe is associated with the sivatherium. So also the suggestion that the hare of Siberia, with its curtailed ears, shorter hind legs, and absence of tail, may be a modification of the ordinary hare, has been answered by Professor Owen, with a reference to the fact that the tailless hare (Lagomys Spelreus) is found as early in the tertiaries as any species of the true genus, Lepus.* Now it is entirely an assumption on the part of those who oppose the transmutation theory, that the original animal shall perish when the new one is produced ; and therefore the difficulty is entirely of their own making. The probable fact is that the modification takes place in an offshoot of the original tribe, which has removed into a different set of circumstances, these circumstances being the cause of the change : thus there is no need to presume that the original tribe is at all affected hy any such modifi .. cation. The case is precisely analogous to that of a colony. 'Ve see, for example. the New Englanders change frorrt the original English type, without any necessary effect upon the parent stock. Just so might the giraffe be a changed sivatherium, and yet the sivatherium continue to exist. And in point of fact, there are many animals now living along with their disposed modified descendants. Unless, therefore, it could be proved that the supposed descendant actually preceded in date the animal from \vhich it was said to have sprung, objections of this na .. tUl'0 can be of no force. The reader will understand that l only adduce the instances of the sivatherium and hare fur the sake of illustration, and without undertaking to • British Fossil Mammalia and Birds, p. 215. |