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Show 1900.] MR. P. P. BEDFORD ON MALAYAN ECHINODERMS. 271 in which an organ takes on the likeness of another organ with which it is in serial homology. This phenomenon, which I have called Homceosis, plays a considerable part in the variations of Meristic series. In plants such variations are common, but in animals instances so striking as that now under consideration are among the greatest rarities in nature. Among Arthropods probably not a dozen examples comparable with the present one are on record. The conversion of antennule into mandible has not hitherto been observed in any form. It should be noticed that the homceosis in the present instance does not transform the appendage into the likeness of the appendage next to it in series, for this is the antenna. The change is to the next but one. Perhaps the cases hitherto known which most nearly approach this one are those of Cimbex and Bombus, having the club of an antenna in each case replaced by a foot. Since the discussion of these cases in ' Materials for the Study of Variation' was written, the new fact has been discovered by Herbst' that when the eye is amputated in Palcemon an antennalike structure may be formed in its place on regeneration. The question therefore arises whether some other Arthropod cases of homceosis may not be similarly connected with regeneration. On this point there is little positive evidence. It may be noted, however, that Przibran2, who made some experiments on the subject, found that in Asellus both pairs of antennas were regenerated as antennas.3 The results of such experiments, however, are clearly very irregular. The regenerated part in Herbst's experiments was not always similar, and Przibran, on repeating Herbst's experiments, obtained only negative results. Here the matter at present rests. 2. On Echinoderms from Singapore and Malacca. B y F. P. B E D F O R D , F.Z.S. [Eeceived March 8, 1900.] (Plates XXI.-XXIV.) The Echinoids and Asteroids described in this paper were collected during a residence of a little over a year in the neighbourhood of Singapore and Malacca by Mr. W . P. Lanchester aud myself. I a m much indebted to the kind courtesy of the Hon. Sir J. A. Svvettenham, Colonial Secretary of the Straits Settlements, aud the Hon. W . Egerton, Eesident-Councillor of Malacca, in allowing us to make use of the lighthouses under their jurisdiction as headquarters for our work; and I a m under a still greater obligation to 1 Arch. f. Entwickelungsmech. ii., 1896, p. 544. 2 Zool. Anz. xix. 1896, p. 424. 3 P.S.-Since this paper was read Mr. L. Doncaster, of King's College, Cambridge, has repeated the experiment on Asellus with the same result. |