THE ZOOLOGIST 
No. 689.—November, 1898. 
BIOLOGICAL SUGGESTIONS. 
ASSIMILATIVE COLOURATION. 
By W. L. Distant. 
(Continued from p. 409.) 
‘Parr II. 
FisH appear to vary in colour and in an assimilative manner 
to the hue of the water in which they are confined.* According 
to Frank Buckland, ‘‘ this is the case particularly with Minnows, 
Sticklebats, and Trout. Mr. Grove, the fishmonger at Charing 
Cross, will tell you where a Trout comes from by its colour. The 
Trout which live in peat-coloured water are sometimes nearly 
black ; those from fine running streams, such as the clear chalk 
* The action of the environment on fishes does not appear to be confined 
to colour alone, According to Prof. Seeley, ‘“‘there are local races of many 
fishes which, under the changed conditions of physical geography, which from 
time to time affect the distribution of life on the earth, have become isolated 
from the rest of the race, so as to live on table-lands or low plains, in cold 
mountain lakes or in shallow swamps, in sluggish waters or rapid torrents, and 
thus, differently circumstanced, have developed into varieties distinguished 
by size, form, colour, and certain internal and external differences in the 
organs and proportions of the body” (‘The Fresh-water Fishes of Europe,’ 
p. 3). Leuciscus muticellus has all the fins “‘ transparent and unspotted in 
Austrian specimens, but in examples from the Neckar the fins of the lower 
part of the body are yellow at the base, and this colour is occasionally seen 
in the dorsal and caudal. Bavarian fish have much black pigment in spots 
on the dorsal and caudal fins” (ib¢d. p. 178). 
Zool. 4th ser. vol. II., November, 1898. 21 
