AN INVISIBLE MONKEY 169 



With regard to the great panda, we have at present no 

 information. It may be suggested, however, that the start- 

 ling contrast presented by its streaks and patches of creamy 

 white on a jet-black ground may harmonise with patches 

 of snow on black rocks, or possibly with the lines of light 

 between the dark stems of forest trees. 



Be this as it may, Dr. Gregory's observations have solved 

 the problem of the use of the remarkable coloration of 

 the guerezas, which has so long puzzled naturalists. Like 

 others of their kind, these monkeys pass most of their 

 time high up on trees, where they sleep either resting on 

 a bough or hanging beneath by their hands, or hands and 

 feet. Now, in the dense forests clothing Mount Kilima 

 Njaro and other districts of East Africa, the black-barked 

 boughs are thickly draped with pendent masses and wreaths 

 of grey beard-moss or lichen, which reach for several feet 

 below them. "As the monkeys hang from the branches," 

 writes Dr. Gregory, " they so closely resemble the lichen 

 that I found it impossible to recognise them when but a 

 short distance away." 



We have thus decisive evidence that the black and 

 white coloration of the guerezas protects these animals 

 by a close resemblance to their inanimate surroundings. 

 There are, however, certain smaller mammals with a 

 similar type of coloration in which the startling contrast 

 of black and white seems to be for the purpose of rendering 

 them conspicuous ; and as some at least of these creatures 

 are endowed with a most disgusting odour, their con- 

 spicuousness has been regarded as warning other animals 

 from attacking them. The best known of these creatures 

 are the ill-famed American skunks, which are in the habit 

 of stalking over the Argentine Pampas in full daylight, 

 with the most consummate indifference to the presence of 



