COLORATION AND MIMICRY 291 



under side serve to render them inconspicuous, from what- 

 ever direction they may be viewed. 



Those who have seen the wooden models of ducks, 

 showing the use of such colouring, in the Natural History 

 Museum at South Kensington, will require no further 

 illustration. 



These models are life size, they are covered with grey 

 flannel, and fixed at some distance from a background 

 covered with the same. 



In one specimen the flannel is left of the same tint as 

 the back ; in the other the flannel has been painted 

 darker on the back, lighter beneath. 



The first one is easily seen, although of the same colour 

 as its surroundings, owing to light and shade. The second 

 has this counterbalanced by tinting, and the result is, that 

 it is quite possible to stand a few feet from it and not see it 

 at all. A brass rail marks the best point for observation. 

 It was only after reading the descriptive card that I was 

 able to perceive the tinted duck at all, and even then was 

 not sure that my eyes were not deceived. 



This dark upper and light under side obtains in all 

 habitually swimming fishes. 



In those that more usually haunt the bottom the colours 

 and markings are those of the bottom. 



The photo of the Dragonet (Fig. 117) illustrates this well. 

 It will be noted that the very size and shape of the markings 

 correspond with the fragments that constitute the shell 

 gravel on which it lives, and the colour in life is precise 

 mottlings of grey, black, buff, or yellow. 



Among the Crustacea I have already mentioned that, 

 while the common shrimp (Crangon) is, as everyone knows, 

 exactly the speckled grey of sand, there are some on one 

 part of this coast that, living where the rocks are diorite 

 and the sand is a coarse mixture of the fragments of the 

 black hornblende and whitish felspar which are its con- 



