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Show [Ch.IV. DIPFICULTI'£8 ATTENDING THE 58 . . . from the mtermtx-and that all intermediate races should spnng ture of those stocks. . ce with all that we d d . holly at vartan This notion, in ee ' ~s w b benomena entitle us to know of hybrid generatiOn; for t efipt somewhat distant, no affirm that had t b e t ypes been at rs d ced much less t h ose ' d have been pro u ' . cross-breeds woul eiJer . as distinct species. b. l now recogmse b b 'd Prolific races w IC 1 we t propagation of y ri to the permanen · In regard, moreove~, bl d'fficulties present themselves, races among animals, msupera. e tbl blending toO"ether of the to concetve e o when we endeavour 't' of two species, so as to . . t nd propenst tes different mstmc s a . diate race. The common t' of the mterme insure the preserva ton t may be protected by the b · d by human ar ' mule, when o tame . 'ld t t it would neither have pre· f . but m a wt s a e, . . power o man ' h r the ass : and If, m con-ants as the orse o cisely tqe same w . . f th' s kind it strayed from the f orne dtfference o 1 ' d sequence o s h t d down by beasts of prey an herd, it would soon be un e destroyed. f insects such as the bee, we f t ke some genus o ' . . I we a pecies has some difference m tts h l of the numerous s 1 find t at eac 1 11 t' honey or constructing its dwe- . . de of co ec mg ' I babtts, Its mo . and other particulars. n 1. roviding for tts young, 'b d b mg, or p h' b the workers are descn e ' y f 1 mmon Ive- ee, . the case o t le co . d d with no less than thuty . d S ence as bemg en owe Ktrby an P ' fi d that amongst a most . t' t * So also we n distinct ms me s · . 1 re nearly as many different 1 s of spiders, t Jere a numerous c as . b there are species. When we f · 'ng thetr we s as modes o spmm . d th relations of these instincts 1 h mphcate are e . recol ect ow co . b h f the animal and vegetable kmg- w.t th co-ext·s t'm g species ' ot 0 . .. that a bastard race cou ld doms, it is scarcely ~ossibfle to Irnf a~::e species and retain just . f the umon o two o ' 't sprmg rom . . f h nt-stock as to preserve Is much of the quahttes o eac pare d. so . f h d ngers which surroun It. ground in sptte o t e ~ few eneric types alone have been We should also ask, tf a . g d' te species have pro· created among insects, and the mterme Ia ,.. Intr. to Entom., vo 1• 1..1 •1 P• 504 ' Ed. 1817, Ch. IV.] PROPAGATION OF HYBRIDS., 59 ceeded from hybridity, where are those original types, combining, as they ought to do, the elements of all the instincts which have made their appearance in the numerous derivative races? So also in regard to animals of all classes, and of plants; if species in general are of hybrid origin, where are the stocks which combine in themselves the habits, properties, and organs, of which all the intervening species ought to afford us mere modifications ? We shall now conclude this subject by summing up, in a few words, the results to which the consideration of the phenomena of hybrids has led us. It appears that the aversion of individuals of distinct species to the sexual union is common to animals and plants, and that it is only when the species approach near to each other, in their organization and habits, that any offspring are produced from their connexion. Mules are of extremely rare occurrence in a state of nature, and no examples are yet known of their having procreated in a wild state. But it has been proved, that hybrids are not universally steril, provided the parent stocks have a near affinity to each other, although the continuation of the mixed race, for several generations, appears hitherto to have been obtained only by crossing the hybrids with individuals of pure species, an experiment which by no means bears out the hypothesis that a true hybrid race could ever be permanently established. Hence we may infer, that aversion to sexual intercourse is, in general, a good test of the distinctness of original stocks, or of species, and the procreation of hybrids is a proof of the very near affinity of species. Perhaps, hereafter, the number of generations for which hybrids may be continued, before the race dies out (for it seems usually to degenerate rapidly), may afford the zoologist and botanist an experimental test of the difference in the degree of affinity of allied species. We may also remark, that if it could have been shown that a single permanent species had ever been produced by hybridity (of which there is no satisfactory proof), it might certainly have lent some (X)Untenance to the notions of the ancients |