Page:The Zoologist, 4th series, vol 3 (1899).djvu/487

Rh As proving the great caution which is necessary before dogmatically asserting anything more than "suggested or probable mimicry" with reference to the preceding instances of simulative resemblances in animals and plants, it may be well to record some cases of what may be considered as

Prof. Semper, when staying in the Balearic Islands, found among the polypes of a coral (Cladocora cæspitosa) Annelids belonging to the genus Myxicola, which lived in long mucilaginous tubes which they had formed in the rifts of the coral. "As long as no light was thrown upon them they protruded themselves just so far as that the top rim of the corona of tentacles was on a level with the tentacles of the polyps, so that the worm and the polyps were both extended; the coral itself presented a perfectly level surface of cups. Moreover, the funnels of Myxicola were of precisely the same chocolate-brown colour as the polyps; and, when fully extended, the interior of the funnel formed by the tentacles looked exactly like the oval disc of one of the neighbouring polyps, for the radial pinnules were in the same position as those lines which, on the oval disc of the polyp, radiate towards the narrow central oval slit; in the Myxicola a small central slit was observable, and all the parts which corresponded so exactly in size and position also displayed exactly the same colouring of greenish grey, with radial lines of a lighter hue and a narrow white streak in the middle. In short, the resemblance in size, position, and colour of every part of the two creatures was so perfect that for a long time I took the corona of the Annelid for a polyp, until, by an accidental blow, I caused all the Myxicolæ of a large coral-stock to shrink suddenly into their tubes, though it was not severe enough to induce an equally rapid movement in the polyps of the apathetic Cladocora." At the time the Professor "felt an almost childish delight at having detected so flagrant an instance of protective mimicry" but soon found reason to doubt this interpretation of the facts. He subsequently found a marine Sponge in which hundreds of this same Myxicola were living, but the Sponge was coloured very differently from the Annelida, so that no protection was offered. Seeking it in other spots, he found the Myxicola almost everywhere, "on the rifts of rocks