236 MOSTLY MAMMALS 



itself, expanding the membrane which joins the feet to the 

 body, like a parachute. The skin is used as an ornament. 

 I think it is identical with one very common in the island 

 of Ceylon, which is almost tame." 



The extraordinary misconception as to the affinities of 

 the creature displayed in the last sentence of this quotation 

 will be apparent when I say that the scale-tailed squirrels 

 — whether furnished with a flying membrane or not — are 

 absolutely restricted to Africa, where not a single repre- 

 sentative of the true flying-squirrels of Asia and Europe 

 exists. 



The reason why these two very dissimilar groups of 

 animals are regarded in popular estimation as near relatives 

 is, of course, due to the fact that both are furnished with 

 expansions of skin by means of which they are enabled 

 to take flying leaps from bough to bough. Such flying 

 membranes are developed in very few mammals, and the 

 popular idea is that the presence of such a membrane must 

 necessarily imply intimate affinity between all the forms in 

 which it occurs. Hence not only are the African flying 

 scale-tailed squirrels associated with the typical flying- 

 squirrels, but the still more widely separated flying-phalangers 

 of Australasia are likewise regarded as members of the same 

 group. 



In making such associations the public fail to recognise 

 that similar structures may be produced in totally different 

 groups of animals owing to their living under similar special 

 conditions, or having peculiar habits of the same nature. In 

 external appearance rodents belonging to different families, 

 such as squirrels and dormice, may be very much alike ; 

 and if certain members of each group had acquired the same 

 mode of life as the flying-squirrels, their similarity would 

 probably have become still more noticeable. For unless 



