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Show 134 DARWINISM CHAP. cases by downy seeds to be wafted th.rough the air, or by hooked or sticky seed-vessels to be earned away, attached to skin, wool, or feathers. Here, then, we have an enormous extension of the region of utility in the vegetable kingdom, and one, moreover, which includes almost all the specific characters of plants. For the species of plants are usually characterised either by diffcr01:ccs in the form, size, and colour of the flowers, or of the frmts; or, by peculiarities in the shape, size, dentation, or arr;tngc ment of the loaves; or by peculiarities in the spines, hairs, or down with which various parts of tho pbnt arc clothed. ] 11 the case of plants it must certainly be admitted that "specific" characters are pre-eminently adaptive ; and though there may be some which are not so, yet all those referred to by Darwin as having been adduced by various botanists as useless, either pertain to genera or higher groups, or arc found in some plants of a species only-that is, are individual variations not specific characters. In the case of animals, the most recent wide extension of the sphere of utility has been in the m;tttcr of their colonrs and markings. It was of course always known that ccrLain creatures gained protection by their resemblance to Lheir normal surroundings, as in the case of white arctic animals, the yellow or brown tints of those living in deserts, ancl the green hues of many birds and insects surrounded by tropieal vegetation. But of late years those cases have been grc<ttly increased both in number and variety, especially in regard to those which closely imitate special objects among which they live ; and there are other kinds of coloration which long appeared to have no use. Large numbers of animals, m.orc especially insects, are gaudily coloured, either with vi vicl I mrs or with striking patterns, so as to be very easily seen. 1\ ow it has been found, that in almost all these ca. c. the crcaJun•: possess . omc special quality which pr 'vents their lH'i11g attacked by the enemies of their kind whenever the peculiarity is known; and tho brilliant or conspicuous colonrs or markings serve as a. warning or signaJ fhtg again. t r.ttl;tck Large number. of insects thus coloured arc n<tusoous aJHl inedible; others, like wasps and bees, have stings; oth ers arc too hard to 1c eaten hy small birds ; while snakes with VI DIFFICULTIES AND 0 BJECTIONS 135 poisonous fangs usually have some characteristic either of rattle, hood, or unusual colour, which indicates that they had better be left alone. But there is yet another form of coloration which consists in special markings-bands, spots, or patches ~f white, or of bright colour, which vary in every species, and arc often concealed when the creature is at rest but di played when in motion,-as in the case of tho bands and spots so frc(]ncnt on the wi~gs and. tails of birds. Now these specific markings are behoved, w1th good reason, to serve the purpose of cnablirw ?ach species to ~e quickly recognised, even at a distance, h~ 1ts fellows, cspccmlly the parents by their young and the two sexes by each other; and this recognition must often be an important factor in securing tho safety of individuals, and therefore the wellbeing and continuance of the species. These interesting peculiarities ·will be more fully described in a future chapter, but they arc briefly referred to hero in order to show that the most common of all the characters by which species arc distinguished from c<tch other- their colours and markings-can be shown to be adaptive or utilitarian in their nature. But be ides colour there are almost always some structural characters which eli. tinguish species from species, and, as regards many of these also, an adaptive character can be often discerned. In birds, for instance, we have differences in the size or shape of the bill or the feet, in the lcn ath of the wincr or t h e ta1' l, an d m. the proportions of the seveb ral fca,thcrs obf which these organs are composed. Alt these differences in the. organs on which the very existence of birds depends, whiCh determine the chai;actcr of flight, facility for rnnnirw or cli~bing, for inhabiting chiefly the ground or trees, and the kmd of food th~t can be most easily obtained for themselves and their offspring, mu. t surely be in the highest ~egrco utilitarian; although in each individual case we, in onr 1gnoranco of the minuti::c of their life-history, may he cp1itc unable to see the usc. In mamma.lia specific differences other than colour usu<.tlly consist in the length or shape of tho cars and tail, in the proportions of the limbs, or in the length and quality of the lmir on difl'erent parts of the body. As regards the ears and tail, one of the objections by Professor |