June 1, 1897.] 



KNOWLEDGE. 



129 



IlLUSTRATED MAGAZINE 



JTERAT 



LONDON: JUNE 1, 1897. 



CONTENTS. 



An Invisible Monkey. B_v R. Ltdbkkee, B.A.Gantab., 



F.K.S. {Ubistraled) 



A Well-loved Haunt. Bv Hahry F. Witheebv (Plate) 

 Progress in Mechanical Science during the Queen s 



Reign. Bt Robert CtORDON Blaike, M.E., Assoc. M. 



Inst.C.E. (Illnslrated) 



Can the Deaf appreciate Music P Bj Dr. J. G. 



McPhersox, F.R.S.E 



The Age of Mountains.— III. By Prof. J. Logan Loblet, 



F.G.S. {Ilhistraied) 



Letters: — W. II. S. Monck; David Flanery 



Obituary 



Notices of Books. {Illi(strated) 



Short Notices ... ... ... 



Books RErEivED 

 Aristarchus and the Sinus Iridum. 



Maunder, F.R.A.S. 

 Day Views of Venus, 



By E. Walter 



(Illustrated) (Plate) 



By P. M. Rttes 



The Swift's Night-Flight. By Charles A. Witchell .. 

 The Language of Shakespeares Greenwood. By 



Cxeobge Mohlet 

 Measurement of the Earth. By A. Fowlee, F.R.A.S. 



(Illustrated) 



The Face of the Sky for June. By H. Sadler, F.R.A.S. 

 Chess Column. By C. D. Locock, B.A.Oxon 



129 

 130 



132 



13.5 



136 

 138 

 139 

 140 

 141 

 142 



142 

 144 

 145 



146 



148 

 151 

 151 



AN INVISIBLE MONKEY. 



By E. Lydekker, B.A.Cantab., F.R.S. 



IN mo3t English dictionariea the verb to " mimic " has for 

 its synonyms "to ape, imitate, counterfeit, or mock"; 

 and it is thus intimately connected with the monkey 

 tribe, whose imitations of human gestures and 

 actions form one of their most prominent charac- 

 teristic features. Till quite recently, naturalists have, 

 however, been totally unacquainted with any instance 

 among these animals of " mimicry " in its scientific sense. 

 That is to say, no case was known where a monkey, for 

 the sake of protection, resembled in form or coloration 

 either some other animal or an inanimate object. During 

 his adventurous journey to Mount Kenya and Lake 

 Barengo, in East Africa, Dr. .J. W. Gregory, of the 

 Natural History Museum, was fortunate enough to make 

 the interesting discovery that the peculiar type of 

 coloration characterizing certain African monkeys is 

 protective in its nature, and that these monkeys, when in 



their native haunts, are thereby rendered practically 

 invisible. 



The monkeys in question (one of which is represented 

 in the accompanying figure) are known to the natives of 

 certain districts of East Africa by the name of " guereza." 

 They belong to the group of thumbless apes (Cololms), which 

 are restricted to the African continent, where they take the 

 place of the langurs, or sacred apes, of India and other 

 Oriental countries. From the other thumbless apes the 

 guerezas (or those species to which that name properly 

 applies) are distinguished by their long, silky, black and 

 white coats, which are much sought after by the natives of 

 Africa as articles of their scanty costume and for purposes of 

 decoration. In the typical Abyssinian guereza the greater 

 part of the fur of the body and limbs is of a deep shining 

 black, but from the shoulders there depends a mantle of 

 long, white, silky hairs, extending down each side and 

 meeting on the lower part of the back, so as to hang down 

 over the sides of the body as well as over the hips and 

 thighs. The terminal third of the tail is also clothed with 

 long white hairs. Strikingly handsome as is this species, 

 it is excelled in this respect by the East African guereza 

 — the one met with by Dr. Gregory — in which the base 

 of the tail is alone black, the whole of the remainder of 

 that appendage being developed into a magniticent whits 

 brush, which may be compared to an Indian cliowri, or fly- 

 whisk. 



Black and white is a type of coloration so conspicuous, 

 and, at the same time, so rare, among the larger mammals, 

 that whenever it occurs we may be quite sure it is developed 

 for some special purpose, although, unless we have an 

 opportunity of seeing the animals in their native haunts, 

 it is almost impossible to divine what that purpose may 

 be. It is met with elsewhere Ln the zebras, and also in 

 the remarkable parti-coloured bear {.FAuropus) of Tibet. 

 Although the former animals are conspicuous enough in a 

 stall at the "Zoo," or when stuffed in a museum, travellers 

 tell us that when seen in the haze of an African desert, 

 their black and white stripes fade at a very short distance 

 to an almost invisible grey. This may even be observed 

 in a hot summer, when the grass is burnt brown, in the 

 Duke of Bedford's seat at Woburn Abbey, where several 

 of these beautiful animals are allowed to i-oam at will in 

 the park during the summer months. 



With regard to the parti-coloured bear, we have at 

 present uo information. It may be suggested, however, 

 that the startling contrast presented by its streaks and 

 patches of creamy white on a jet black ground, may har- 

 monize with patches of snow on black rocks, or possibly 

 with the lines of light between the dark sterna of forest 

 trees. 



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

 solved the problem of the use of the remarkable coloration 

 of the guerezas, which has so long puzzled the brains of 

 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-stemmed trees are thickly draped with 

 pendant masses and wreaths of grey beardmoss, or lichen, 

 which reach for several feet below the boughs. "As the 

 monkeys hang from the branches,'' writes Dr. Gregory, 

 "they so closely resemble the lichen that I found it impossi- 

 ble to recognize 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 



