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Show CHAP. IT. DOUBTFUL SPECIES. 50 ··rt they can be crossed that most careful observer G~ner, ld hardly wish fol· only with much difficulty. £ e c~:ing specifically disbetter evidence of the two o::s are united by many tinct. On the other h.a-r:d, eyd btful whether these intermedi.a te 1I' n1 r s, an d It IS ver.y osu i t seems to me, an b 'd . nd there IS, a h links are hy ri s ' a · ental evidence, s ow- overwhelm.i ng amo unt of expenmm on parents, and con- . that they descend from com. . Ing k d as varieties. . sequently must be ran. e t es will bring naturalists . . t' Inmos cas ' . Close Investiga wn, k d ubtful forms. yet It t how to ran o . to an agreemen . . . the best-known countnes must be confessed, that It IS In b of forms of doubtful fi d th greatest num er · that we n e k with the fact, that 1f any value. I have been struc f ture be highly useful . 1 t . n a state o na . . arumal or p an I 1 ely attract h1s attentiOn, to man, or f rom a ny cause c.o s lly be found recorded · . f •t ·n lmost universa varieties o. I. WI a . will be often ranked by some These varieties, moreover,k t the common oak, how authors as spec· ies · Lood i da . yet a German auth or closely it has been stu e ' . out of forms which h d zen speCies ' . makes more t an a o . d d as varieties . and in this are very generally c~sl e~e 1 authorities ~nd practical country the highest o~nlc~h t the sessile and pedunmen can be quoted ~o s ow : d distinct species or culated oaks are either goo an mere varieties. . mences the study of a When a young naturalist com . h . t :first . . t unknown to him, e IS a group of organisms qm e . h t differences to consider much perplexed to determin.e t': a. .!'or he knows nothing ':fi d hat as val'le 1es , 1' as speCI c, an w d k' d f . t' to which the group 0 vana 1on of the amol1nt an . In t 1 t how very generally is sub~ect; and t~s. show~~ ife~: ~onfine his attention there IS some vanation. u h ·n soon make up to one class within one countr~ ~ w~tful forms. llis his mind how to rank most of t e ou CHAP. II. DOUBTFUL SPECIES. 51 general tendency will be to make many species, for he will .become impressed, just like the pigeon or poultryfancier before alluded to, with the amount of difference in the forms which he is continually studying; and he has little general knowledge of analogical variation in other groups and in other countries, by which to correct his first impressions. As he extends the range of his observations, he will meet with more cases of difficulty ; for he will encounter a greater number of closely-allied forms. But if his observations be widely extended, he will in the end generally be enabled to make up his own mind which to call varieties and which species; but he will succeed in this at the expense of admitting much variation,-and the truth of this admission will often be disputed by other naturalists. When, moreover, he comes to study allied forms brought from countries not now continuous, in which case he can hardly hope to find the intermediate links between his doubtful forms he will have to trust almost entirely to analogy, and his' difficulties will rise to a climax. Certainly no clear line of demarcation has as yet been drawn between species and sub-species-that is, the forms which in the opinion of some naturalists come very near to, but do not quite arrive at the rank of species; or, again, between sub-species and well-marked varieties, or between lesser varieties and individual differences. These differences blend into each other in an insensible series; and a series impresses the mind with the idea of an actual passage. Hence I look at individual differences, though of small interest to the systematist, as of high importance for u~, as being the first step towards such slight varieties as are barely thought worth recording in works on natural history. And I look at varieties which are in any degree more distinct and permanent, as steps leading to more D2 |