NATURAL SELECTION 241 



the pattern was not protective as the fishes were very conspicu- 

 ous, and they were more obviously protected by their agility 

 and their habit of keeping close to the coral-rock labyrinths. 

 Reighard held that the patterns had no evident value as of 

 warning or aggressive significance, nor as having been due to 

 sexual selection. It must, however, be remembered that the 

 Grey Snapper is probably only one of many enemies of the 

 coral fishes. 



Colours of arctic and subarctic mammals, etc. 



The change to a white winter pelage has always been 

 regarded as an adaptation to the snowy landscape, less generally 

 as a means of conserving heat. That the coat-colour of some 

 forms bears a steady relation to the type of background is, we 

 think, quite clearly seen in such forms as the Stoat, which 

 does not have a pale moult in the south of the British Isles 

 but shows it in the north. In the Stoat the pale moult is not 

 directly influenced by climate, as it is found to take place 

 sometimes in early autumn and is occasionally found in 

 southern forms. 



A still more interesting case is that of the subspecies Putorius 

 nivalis monticola, which has a pale moult in winter, even when 

 living at low altitudes along with the typical dark form (Cuenot, 

 1921, p. 311). 



The incidence of the pale moult in subarctic regions is 

 very instructive, and at the same time appears somewhat para- 

 doxical. The Lemming has no moult (Hinton, 1926), nor 

 have the Rabbit, the Pine Marten nor the Common Fox, at 

 least in the north of the British Isles. On the other hand, the 

 Weasel, Stoat and Varying Hare show the change. Possibly 

 the habits of these animals may serve to explain the difference. 

 Thus the Pine Marten is a forest animal, and the Rabbit 

 tends to feed near its warren, to which it has a rapid escape. 

 But the Fox ranges into the same terrain as the protected (?) 

 Varying Hare. The Lemming is a burrowing animal, and 

 in winter may live under the snow. 



Instances might be accumulated of mammals with an 

 extensive range from warm into cold climates which exhibit a 

 change towards paler colour in the northern part of their 

 range (tigers (Pocock, 1929)). Whether this tendency is 

 adaptive in origin or due to climate it is impossible to say, but 



