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Show 76 DARWINISM OllAP. two yen.rs the sparrows began to attack them, and thereafter destroyed them quite as readily as the yellow ones ; and he believes it was merely because some bolder sparrow than the rest set the example. On this subject Mr. Charles ~· Ab~ott well remarks : "In studying the habits of our Arr:encan birds -and I suppose it is true of birds evcrywh~r~-~t must at ~11 times be remembered thn.t there is less stabihty m the hab~ts of birds than is usually supposed ; an~ no acco~nt of the habits of any one species will exactly detail the v~rwus features ~f its h~Lbits as they really arc, in every portiOn of the tern-tory it inhabits." I • Mr. Charles Dixon has recorded a remarkable chan~e m the mode of nest-buildinrr of some common chaffinches whiCh were taken to New Zealanbd and turned out there. lie says : " The cup of the nest is small, loosely put together, apparently lined with feathers and the walls of the structure are prolonged for about 18 in~hes, and hang loosely down the side of the supporting branch. The whole structure b~ars so~e r esemblance to the nests of the hangnests (Ictendre), w1th the exception that the cavity is at the top. ~learly these ~ ew Zealand chaffinches were at a loss for a design when fabncatino- their nest. They had no standard to work by, no nests of th~ir own kind to copy, no older birds to give them any inst~·uction and the result is the abnormal structure I have JUSt desc'r ibed." 2 These few examples are sufficient to show that both the habits and instincts of animn.ls are subject to variation; a.nd had we a sufficient number of detailed observations we shonl<l probably find that these va~iations were as n':merous, as diverse in character, as large m amount, and as mdcpcnd~n t of each other as those which we have seen to characten se their bodily structure. The Variability of Plants. The variability of plants is notorious, being proved no~ onl! by the endle ·s variations which occur whenever a sp~c.ICs Is lar()'ely O'rown by horticulturists, but also by the grea,t difli culi y that is f~lt by botanists in determining the limits of species i11 1 Nctlttre, vol. xvi. p. 163; aJHl vol. xi. p. 227. 2 Ibid., vol. xxxi. (1885), p. 533. ru VARIABILITY OF SPECIES IN A STATE Off NATURE 77 mn.ny large genera. As exn.mples we may tn.ke the roses, the brambles, and the ·willows as well illustra,ting this fact. In Mr. Baker's Revision of the Br·itish Roses (published by the Linncan Soc~cty in 1 G 3), he includes under the single species, Rosa camna-the common dog-rose-no less than twenty-ei()'ht named Vltrieties distinguished by more or less constant charact~r and often confined to special localities, and to these arc referred about seventy of the species of British and continental bollanists. Of the genus Rubus or bramble, jive British specie arc given in Bentham's Iflmdboolc of the Briti h Flom, while in t~e fifth edition of Babington's Mnnual of B1·itish Botany, pubbshed about the same time, no less than forty-jive specie. are described. Of willows (• 'alix) the same two works enumerate fifteen and thirty -onP species respectively. The hawkweeds (Hieracium) are equally puzzling, for while Mr. Bentham n.dmits only seven British species, Professor BabinO'ton describes no less than thirty-two, besides several named varieties. A French botanist, Mons. A. Jordan, hn.s collected.numerous forms of a common little plant, the spring whitlow-gra. s (Draba verna) ; he has cultivated these for several succe. sive years, and declares that they preserve their peculiarities unchanged; he also says that they each come true from seed, and thus possess all the characteristics of true specie . He has described no less than fifty-two such species or permanent varieties, all found in the south of France ; and he ur()'es botanists to follow his example in collecting, dcscribin()', a~d cultivating all such varieties as may occur in their rcsp~ctivc districts. Now, as the plant is very common aJmo t all over Europe and mngcs from North America, to the Himalayas, the number of similar forms over this wide nrca would probably have to be reckoned by hundreds if not by thousands. The class of facts now adduced mu t certainly be held to prove that in many large genera and in some single species there is a very large amount of variation, which renders it quite impossible for experts to agree upon the limits of species. We will now adduce a few striking cases of individual variation. The distinguished botanist, Alp. de Canclollc, nmdc n special study of the oaks of the whole world, and has stated some |