532 



NATURE 



[October 27, 1910 



ART THE COMRADE OF SCIEXCE.' 



IT has long been known that Mr. A. H. Thayer, the 

 discoverer of the great principle of countershad- 

 ing in nature, was preparing a fully illustrated exposi- 

 tion of his observations and theories, and that his son 

 was helping him in the enterprise. The present beau- 

 tifully illustrated and finely printed work is the result. 

 The great discovery of the obliteration of apparent 

 solidity by means of countershading, first published 



Fig. I. — Plymouth Rock Hen, lacking countershad.ng, and 

 therefore conspicuous against a background of Plymouth 

 Rock skins. 



in 1896 (The Atik, vol. xlii., pp. 124 and 318), was 

 convincingly illustrated in this country by the models 

 prepared by Mr. .\. H. Thayer, and presented to the 

 natural history museums of London, 0.\ford, and 

 Cambridge. .An account of the principle, as well as 

 the description of the Oxford model prepared 

 bv the present writer, appeared in Nature for 

 April 24, 1902 (vol. Ixv., p. 596). 



After the great and \vide-reaching discovery 

 which has probably been accepted by all 

 naturalists who have studied it, the author has 

 £jradually extended his conclusion that the 

 colours of animals are adapted for concealment, 

 and carried it into regions where a very dilTerent 

 interpretation had been accepted. Thus in his 

 papers in the Transactions of the Entomological 

 .Society of London (1903, pp. SS3"569)> and in 

 the Popular Science Monthlv (December, 1909, 

 p. 550), Mr. Thayer maintains that appearances 

 which have been explained as warning, mimetic, 

 and sexual are to be interpreted by the one 

 dominant and universal principle of conceal- 

 ment in nature. .It cannot be said that, in 

 these, later developments, Mr. Thayer has suc- 

 ceeded in convincing any large number of 

 naturalists, and it is therefore of especial im- 

 portance that a detailed, complete, and fully 

 illustrated statement should have appeared in 

 the present volume. 



The great bulk of the work, which opens 

 with an introductory essay, dated 1907, by Mr. 

 A. H. Thayer, is occupied, first, by a full and 

 admirable exposition of the principle of 

 obliterative shading and the combination with 

 it of "picture patterns," and secondly, by a 

 sketch of the distribution of these methods of con- 

 cealment throughout vertebrate animals and insects, 

 the birds being treated in far greater detail than any 



1 ** Conceal'ng-Color.ition in the Animal Kingdom." An Exposition of 

 the Laws of Disgni^e through Colour and Pattern ; being a .Summary of 

 Abbott H. Thayer's Discoveries. By Gerald H. Thaver. With an Intro- 

 duclory Essay bv A. H. Thayer. (New Vork : The Macmillan Co. ; 

 London: Macmillan and Co., Ltd., lycg.) Price 31J. f d. net. 



other group. Mr. Thayer's later views are not ex- 

 pounded separately, but are to be found scattered in 

 various parts of the volume, which must be carefully 

 studied as a whole by any reader who would do 

 justice to the author and his father. 



The value of obliterative countershading is well 

 illustrated by figures of two breeds of fowl in which 

 it is lacking. However closely such fowls may har- 

 monise with the colour of a flat background, they 

 must be rendered conspicuous against it by means of 

 shadow, as is at once obvious in Fig. i. 



A series of interesting photographs of models makes 

 it clear that obliterative shading is even more 

 important than markings for the purpose of conceal- 

 ment. Thus, the model in Fig. 2 represents a rela- 

 tively inconspicuous gap in the pattern of the back- 

 ground ; that in Fig. 4, possessing the pattern, is by 

 comparison a strikingly distinct and solid object. We 

 are thus led to conclude that the perfect obliteration 

 represented in Fig. 3 depends in larger measure upon 

 the principle illustrated in Fig. 4 than upon that 

 shown in Fig. 2. 



The vast importance of this same principle is 

 demonstrated, not only by diagrams, but by large 

 numbers of representations of actual animals to be 

 found in later pages of the work. .A striking example 

 is .seen in Fig. .s, where the animal has been photo- 

 graphed in a position which reverses the obliterative 

 tendency of its colouring in the normal position. We 

 here get maximum conspicuousness — the lightest tint 

 in the strongest light, the . darkest in the deepest 

 shadow. 



The relation of the pattern to perspective is dis- 

 cussed in an extremely interesting and original section 

 (chapter iii.), where the conclusion is reached that 

 " the obliteratively shaded surface must bear a picture 

 of such background as would be seen tlirough it if it 



TTy^m 





V-' 



' '\<>'/l 



-l;ira-sh.ii>e.l S.,l„l M. 

 ligh'.ed, but 



ol.liter.itively sh.id,.d in full 

 aled by the want of pattern. 



were transparent." This is well illustrated by the 

 diagram shown in Fig. 6, where the smaller pattern 

 of the highest part of the bird is seen against the 

 receding, and therefore to the eye diminished, details 

 of the background. 



Mr. Thaver discriminates sharplv between all such 

 obliterative coloration depending on countershading 

 combined with background picturincr, and mimicry, or 

 tlie simulation of a solid object. He truly points out 



NO. 2139, VOL. 84] 



