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Show [CliAP. VIII. HYBRIDISM. 240 ked line of d1' s t'1 nc~ strong wish was ~o draw a . u:~ could find very few tion between speCies and. vane. p'ortant differences beand as it seems to me, qu~le ffi1m·ng of species, and the twe~n the so-called :1 b;lnO' o o/p~~rieties. And, on ~he so-called mongrel o sp o t losely in very many liDother hand, they agree mos c portant 1,espects.. th' ub' ect with extrenie brevity. I shall here d1scus~ . lS ~ ~. that in the first gener- The most ilnportant dlstinct~.o~{:'than hybrids~ but Gartation mo?grels are mo:e svf~·:m s ecies which 'have long ner admitS that hybfld . bl~ in the first ~eneration; been cultivated srff o ten v~ykinO' instances of this fact. and I have royse ~een \\1 brlds between very close~y Gartner further admits tha. bl than those from very dis-allied spe?ies are d~l:e hrlas that the difference in the detinct specieS ; an t IS s ow When mongrels and gree of varia~ility, g~aduates away.ated for several gener-th~ more fertile hybnds are l~~fa\nity in their o~spring ations an extreme amoun} o ases both of hybnds and is notorious; but .s~me 01 ~ity of character could be mongrels long r~thl~~g ~~~~~er in the successive gener-given. The varia ~ 1 y, ;eater than in hybrids. atiollfa of mongrels 1~, til-~apsf ~ongrels than of hybrids This greater varia 1 Y 0 t e at all surpns· 1· ng. For the par. en. ts does not see1n om . t' nd mostly domestic vanetles of mongrels ar~ varle Ies, . a been tried on natural vari- (v~ry fewd e:li:li:pen: f:v:gst cases tha~ there has been cties), an . . . . d therefore we might expect that recent v~na?;hty ' l~ ften continue and be superadded such vari~~Ihty wou o act of crossing. The slig~lt to that arlsln~ fr_o~ t~e mer~ids from the first cross or m degree of vanab~hty ;n hy~ t with their extreme variathe first generation, In con ras . . urious fact and bility in the su?ceediFg ~~n~~~~~n;~1!:d ~orroborates the deserves attention. t ~r 1 the cauQe of ordinary varia~ view which I have ~ ~non h ""'~ roductive system bility ; namely, that ~t.1s due to ~h:~~ in the conditions bein~ eminently sensitive to dny d 'ther impotent or at l!a~! {u~:~:~1!1~f ~!;e;r~~~r ef~cti~n of producing off- CHAP. VIII. I HYBRIDS AND MONGRELS. 241 spring identical with the parent-form. Now hybrids in the first generation are descended from species (excluding those long cultivated) which have not bad their reproductive systems in any way affected, and they are not variable; but hybrids thmnselves have their reproductive systems seriously affected, and their descendants are highly variable. But to return to our comparison of mongrels and hybrids : Gartner states that mongrels are 1nore liable than hybrids to revert to either parent-form ; but this, if it be true, is certainly only a difference in degree. Gartner further insists that when any two species, although most closely allied to each other, are crossed with a third species, the hybrids are widely different from each other; whereas if two very distinct varieties of one species are crossed with another species, the hybrids do not differ much. But this conclusion, as far as I can .make out, is founded on a single experiment; and seems directly opposed to the results of several experiments made by Kolreuter. These alone are the unimportap.t differences, which Gartner is able to point out, between hybrid and mongrel plants. On the other hand, the resemblance in mongrels and in hybrids to their respective parents, more especially in hybrids produced from nearly related species, follows according to Gartner the same laws. When two species are crossed, one has sometimes a prepotent power of im· pressing its likeness on the hybrid ; and so I believe it to be with varieties of plants. With animals one variety certainly often has this prepotent power over another va· riety. IIybrid plants produced from a reciprocal cross, ·generally resemble each other closely; and so it is with mongrels from a reciprocal cross. Both hybrids and mongrels can be reduced to either pure parent-form, by repeated crosses in successive generations with either parent. These several remarks are apparently applicable to animals; but the subject is here excessively complicated, partly owing to the existence of secondary sexual charac~ ters; but more especially owing to prepotency in trans- 11 |