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Show 154 MR. R. MELDOLA ON VARIABLE PROTECTIVE [Feb. 4, " survival of the fittest," it is perhaps scarcely necessary to add. Notwithstanding this identity of origin, I would venture to suggest the propriety of confining the application of the word " mimicry " to such cases as those to which it was first applied by M r . Bates- to those, viz., in which the object imitated is animate; while the expression " protective resemblance" should be restricted to those cases in which the object simulated is inanimate or part of a vegetable structure. This distinction is, I a m persuaded, well adapted to prevent that confusion of ideas which is apt to arise when the term " mimicry " is used in the sense in which it has been recently used by Dr. Hagen, whose paper, designated " Mimicry in the Colour of Insects"*, contains in reality no cases of mimicry at allf. The distinction here enforced was adopted by M r . A . R. Wallace in his well-known essay published in the ' Westminster Review' for July 1867, but it appears to have been neglected by most subsequent writers on the subject. Classification of the cases of protective resemblance. In every case of protective resemblance the disguised species simulates some object in the environment; and as the object thus imitated m a y be of a nature either constant or variable, we are obviously provided with a means of classifying the cases of protective resemblance, though but imperfectly, according to the stability of the characters of the imitated object. As the result of an attempt to arrange the cases of protective resemblance according to this system, I have found it necessary to erect the four following classes, which include, so far as I know, all the known cases, with the exception of a certain small group which will be considered hereafter :- I. Cases in which both the characters of the imitated object and the disguising characters of the species remain constant during the lifetime of each individual. This class includes a very large proportion of the known cases of protective resemblance, and passes by small gradations into Class II. Most of those instances in which there is mere harmony of colouring between a species and its environment belong to this class. II. Cases in which the imitated object varies within certain small * ' American Naturalist' for July 1872. t It will be well here again to insist upon the fact, previously insisted upon by Mr. Wallace, that the word mimicry is not to be understood in the sense of voluntary imitation. It is true that in many cases the mimicker copies its model in mode of flight or other habits; but even here the imitation cannot be considered voluntary, since such modification of habit has most probably arisen by the natural selection, through many generations, of individuals whose manner of flight resembled in any way the manner of flight of the imitated species-just in the same way as this agency, selecting through many generations those individuals whose colour, form, pattern, &c. approached in any way the colour, form, or pattern of the imitated species, has at length brought about the close resemblance in external characters which we now behold: in other words, along with the structural there has gone on a psychical mimetic adaptation. |