II. SUPPOSED EVIDENCE OF MUTATION IN MALTHOPSIS. 
Among the collection made by the “Investigator” are four small communities 
of pediculate fish of the genus Malthopsis , from separate but not far distant stations 
in the Andaman Sea. 
It has been the custom in the Indian Museum to regard these four communities 
as of one species — M, luiea — although the individuals are so variable that if certain of 
them had been found alone in separate localities they would have been regarded 
without doubt as distinct species. However, they have been looked upon as one 
species, partly because each group was taken at one cast of the trawl in similar circum- 
stances, ever}’ individual being of the same remarkable yellowish pink colour; but the 
fact that individuals of a particular and constant type occurred in the first three 
commimities obtained, was probably the chief reason for regarding the whole collection 
as one species. This particular type predominated in the first community and it was 
described and figured as the type of the species. It was at first thought that the great 
variation shown by some members of the first community was due to the fact that 
they were immature. It was subsequently made clear, when the other communities 
were obtained, that the characters which were at first thought to be due to immaturity, 
occurred in some adult forms. There are twenty-one specimens in all and it will be 
shown that there are five distinct types among them not linked by intermediate forms. 
The four communities will be designated by the letters A, B, C and D, the five types 
by the letters v, w, x, y and z. The types are distributed in the following way; the 
figures indicate the numbers of individuals of each type : — 
Community A contains 2 v, 2 w, x. 
,, B ,, V, 6w. 
,, C „ V, w, 2 y. 
,, D ,, 3 w, 2 z. 
Type V occurs in three of the communities, while w occurs in all four. A speci- 
men of type V was figured as M. lutea, for this type predominated in community A, 
which was the first to be obtained, and from which the genus and species were 
defined. 
Two years ago I drew up a description of the type z under the name 
Malthopsis triangularis. There is no doubt that’ this type, of which there are two 
specimens, is remarkably different from the type v. The description is published 
here {antea) for the first time, though it seems that the other types w, x and y have 
almost as good a claim to specific rank. 
