!sov. 11, 1881.] 



KNO^A^LEDGE 



21 



AN ,li 



LTRATED 



MAGAZINE OF SCIENCE 

 plainlyWorbed -ExactMescribej 



LONDOX. FRIDAY, XOVEMBER 11, ISSl. 



CONTENTS. 



FAGR 



i The Fiji Islands 31 



CoREEspoNBENCB. — Th© One -inch 

 Map of the Ordnance Surrej— Is 

 the Sun Hot ?— Influence of Sei on 

 Mind— November Meteors, &c. ... 35 



PAGE 



The Philosophy of Animal Colours. 



By Dr. Andrew Wilson, P.E.S.E . 21 

 The South European Volcanic System 32 

 The Relation of Food to Muscular 



Work.— Part II. By Dr. W. B. 



Carpenter, F.H.S 23 i Queries Jo 



Brain Troul.les 2.5 Unhealthy Houses 39 



Comets. Part \l.— (Illutlr<Ued) 26 i Plain Words in Science 39 



IntelliKence in Animals 23 I Trusting to Luck 39 



Birds with Teeth (lUiufraUi) 30 ' Our Chess Column 41 



The Southern Skiea in November— | Our Wliist Column. By " Five of 



(niutlraUd) 31; Cklbs " 42 



THE PHILOSOPHY OF ANIMAL 

 COLOURS. 



By Dii. Andrew Wilson, F.R.S.E. 



THERE is a suggestive passage in Butler's " Hudibras," 

 which maintains that — 



" Fools are knoini by looking wise, 

 As men find woodcocks by their eyes." 

 And if the axiom be correct, that a poet is only great 

 •when he is true to nature, it must be admitted that Butler 

 has been singularly felicitous in this metaphor. Whoever 

 has seen a woodcock in its ordmary summer plumage may 

 form a good idea of the truth of the poetic remark. As 

 that bu-d moves about amongst the fallen leaves of autumn, 

 the greys, and browns, and yellows of its feathers mingle 

 so beautifully with the like tints of its surroundings, that 

 the animal is absolutely concealed from any view but the 

 practised eye of the sportsman. As has been remarked of 

 the bird in question, oven the very conspicuous and orna- 

 mental tail becomes hidden from \-iew in a most singular 

 fashion. Below, these tail-feathers e.xliibit a white colour 

 tinted with a silver sheen and marked with a deep black. 

 Nothing more conspicuous than such an ornament can v\-ell 

 be imagined ; yet the tail and its belongings are, neverthe- 

 less, wonderfully concealed. For, as the bird reposes, these 

 under lines and tints are placed downwards ; and al)o\e, 

 the ashen-grey tints mmgle perfectly with the bird's sur- 

 roundings. As the woodcock, therefore, rests amid its 

 background of wood and its foreground of fallen leaves, 

 every line of its plumage is made to assimilate so closely 

 witli the objects around, that the bird's presence, even a 

 short distance off, is not suspected. 



The woodcock is by no means alone in this liarmony 

 betwixt its plumage and its surroundings. The sand- 

 grouse of the deserts, for instance, exliibit a like harmony. 

 These birds cannot be detected, even as they run, amidst 

 the sand of their haunts — so closely imitated in the dull 

 tints of their plumage is the tone of the desert wild. The 

 well-known case of tlie ptarmigan is even more extraordi- 

 nary still. In summer the bird shows a plumage of pearly 

 grey, which conceals it perfectly as. it lies on its bed of 

 Scottish heather, mingled with the lichen and its kith and 

 kin. But when the winter snows descend and coat the 

 hillsides with a mantle of white, then a kindlv nature 



still contrives concealment for the ptarmigan in a fresh 

 suit of colour. The pearly greys of the summer are re- 

 placed by a plumage of snowy whiteness, and, save for its 

 dark eye, there is little risk of the discovery of the bird by 

 the unwary or unpractised sportsman. The grouse and 

 common partridge are not less perfectly protected. The 

 lines of the grouse match the tints of the heather, and the 

 cartridge is almost as difficult to discover — say, in a ploughed 

 tield — as the ptarmigan on the hill-side. The birds just 

 mentioned are all rasorial birds ; that is, they are 

 allied to the type of the common fowl, and are typically 

 ground-livers. " Their tints, therefore, assimilate with those 

 of the ground and with ground vegetation ; and whatever 

 may be the ultimate philosophy which shows the origin of 

 such harmonies, it is very plain that the utilitarian is 

 bound to read "protection" in eveij line of the story. 

 Escape from their enemies must be favoured by the corre- 

 spondence in colour to which we allude. The harmonies of 

 colour present the safest, and therefore the best foil, to the 

 keenness of sight of the eagle, and to the agility of the 

 falcon and its kind. It is difl'orent, indeed, with the 

 songsters of the wood and grove. With well-developed 

 powers of flight, and with a close refuge amid the foliage 

 of the wood, the appearance of bright hues and tints in 

 these birds is by no means disadvantageous. Another law 



that of the development of colour in relation to sex — 



has taken precedence of the regulation of colour as a means 

 of protection. If concealment be necessary, nature wOl 

 teach the art of hiding in other ways than that whereby 

 she contrives to make the partridge face danger with a 

 stillness that almost rivals that of the stones, trustful in 

 the harmony of her plumage that so closely matches her 

 heather bed. 



But there are wider fields open to the naturalist's survey 

 of colour and its meanings. Suppose that we peer for a 

 moment into the class of fishes, we shall find the adapta- 

 tion of colour to surroundings illustrated in a very apt 

 decn-ee. Whoever has tried to spear a sole or flounder, for 

 example, well knows that the excitement of the sport 

 consists in the endeavour to follow out the axiom of Mrs. 

 Glasse, and on the principle which that worthy lady laid 

 down about " first catching your hare," to first catch your 

 flounder. You cautiously and softly paddle out to shallow 

 water in your punt, and you drift over the flat, sandy 

 beach at a depth of from two to three feet. Below, the 

 water is as clear as crystal. Here and there you see a 

 lazy starfish on the march, exerting himself to the utmost, 

 as he slowly extends ray after ray, and crawls at the rate 

 of about a mile a month or so, by aid of his hundreds of 

 sucker-feet. The sand-eels annoy you as they burrow 

 dowaiwards and send up little clouds of dust on your 

 approach ; but the floimders you came to spear — where 

 are they 1 and echo seems but to answer " Where 1" 

 But the practised sportsman bids you learn (as in all other 

 sciences and arts) the first lesson — namely, how to see and 

 observe. As your boat creeps along, he points to what 

 seems a mere sandy lump, but 'm. which his keener eye has 

 detected the merest wriggle of a fin. Dash ! goes the 

 spear, and up comes a flounder, and as you watch the 

 <n-ound, you see dozens, it may be, of similar sandy patches 

 swimming off in rapid alarm. The flounder's " back " — 

 it is really the side of the fish — on which it lies, is white 

 enouo-h, as we know ; but the " other side " is as close a 

 representation of a sandy patch as you can see or as you 

 can imagine. Small wonder, then, that in flounder- 

 spearing you experience the difficulties which nature 

 throws in the way of capture through likeness in colour 

 to the animal's surroundings. It is the same with sole , 

 turbot, and with the skates and angel-fishes. Watch th'. 



