1900.] MB. F. P. BEDFOBD ON MALAYAN ECHINODEBMS, 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 antenn.ule 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 ap- 

 pendage 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 1 that when the eye is amputated in Palcemon an antenna- 

 like 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 Przibran 2 , who made some experiments on the subject, 

 found that in Asellus both pairs of antennae were regenerated as 

 antennae. 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. 

 By F. P. Bedfobd, 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 neigh- 

 bourhood of Singapore and Malacca by Mr. W. P. Lanchester and 

 myself. 



I am much indebted to the kind courtesy of the Hon. Sir J. A. 

 Swettenham, Colonial Secretary of the Straits Settlements, and the 

 Hon. W. Egerton, Resident-Councillor of Malacca, in allowing us 

 to make use of the lighthouses under their jurisdiction as head- 

 quarters for our work ; and I am under a still greater obligation to 



1 Arch. f. Entwickelungsmech. ii., 1896, p. 544. 



2 Zool. Anz. S5x. 1896, p. 424. 



3 P.S. — Since this paper was read Mr. L. Doncaster, of King's College, 

 Cambridge, has repeated the experiment on Aaellus with the same result. 



