246 PROF. s. J. HicKSON ON THE [Apr. 5, 



look tor auy explauatiou of these colour-variations, aud that their 

 wonderful differences rendered useless any stud}' of them for 

 systematic purposes. But further consideration seemed to show 

 that all the variations, diverse as they were, might be explained by 

 the combined influences of albinism, melanism, erythrism, and 

 xanthism on a natiu'ally Aariable species. In the present series 

 melanism did not occur, as it did in some of the other described 

 forms ; but a greater or less degree of albinism might easily be 

 responsible for the whitening of the muzzles, ears, feet, bellies, 

 tails, and ultimately of the whole animal, and erythrism for the 

 different degrees of red present on different specimens. Finally, 

 xanthism, of which the best known instance was the common buff- 

 coloured variety of the Mole, might be responsible for the buffy 

 washing on the tail of specimen no. 5 described above. 



If this explanation were correct, we should, after the elimination 

 of the affected specimens, be able to look upon example no. 1 as 

 the normal primitive form the colour of which might be accepted 

 for comparison with that of allied species, just as if S.Jinlat/soni 

 were no more variable than other Squirrels. A similar sort of 

 elimination had to be practised in studying European Squirrels, 

 among which the many individuals affected with melanism had to be 

 withdrawn fi'om consideration before any satisfactory study could 

 be made of the local coloration. 



Erythrism in Mammals, and especially in Squirrels ', had often 

 been observed before, while in combination with albinism it 

 bad been found to present an explanation of the remarkable 

 colour-phenomena occurring in the Spotted Cuscus {Phalanger 

 maculatus) ^. 



The following papers were read : — 



1. Ou the Species of the Genus Millejjora : a preliminary 

 Communicatiou. By Sydney J. Hickson^ M.A,, D.Sc, 

 F.R.S., F.Z.S. 



[Received April 5, 1898.] 



The phylum Coelentera presents us with many families and 

 orders of animals in which our knowledge of the characters 

 which can be satisfactorily used for the purpose of systematic 

 classification is singularly deficient. In the Madreporaria, the 

 Grorgonacea, and the Milleporidje the form of growth of the 

 colony, the colour, aud the structure of the hard skeletal parts are 

 the only characters which have been used for the diagnosis of 

 genera and species. In many cases it is probable that the 

 diagnosis afforded by these characters should be considered to be 

 satisfactory, but as the number of specimens in our museums 



1 Cf. P. Z. S. 1886, p. 77. 



2 Oat. Marsup. B. M. p. 199 (1888). 



