October 27, 19 10] 



NATURE 



533 



that the goal of the first principle is invisibility, of 

 the second deceptive 7'isibility. "The latter principle 

 is open to unlimited variations of method and result, 

 whereas the former ... is in its main essentials 

 strictly limited. There are innumerable kinds of solid 



possessing a patlern like tliat of the backfjiounti. 



objects for animals to simulate in appearance, but 

 there is only one way to make a solid object in a 

 natural lighting- cease to appear to exist " (p. 25). 



The use of the term " mimicry " to indicate the 

 second category, although common, is to be 

 deprecated. It is inconvenient to apply the 

 same term to the resemblance of a moth to a 

 wasp, and that of a caterpillar to a twig. The 

 wasp-like moth is always spoken of as an 

 e.\ample of mimicry; and the term imitatiim 

 mav be conveniently used in a technical sen^. 

 to include the twig-like caterpillar and all tin 

 other innumerable e.xamples of special protec- 

 tive resemblance. The important classific.i- 

 tion of cryptic resemblances, which Mr. 

 Thayer now establishes more thoroughly and 

 correctly than before, may be appropriately 

 expressed by the use of the terms (i) oblitera- 

 iive or afihaniatic coloration, and (2) imitative 

 or cikonic resemblance. 



No fewer than sixteen out of the twenty- 

 seven chapters of the book are concerned with 

 the colouring of birds, the patterns being 

 classified according to the nature or distance 

 of the background that is pictured. A vast 

 amount of patient and loving observation of 

 nature is here summed up and expressed. \\'e 

 shall look forward with the deepest interest 

 to the comments of those special students of 

 bird-life in Europe and .America, who will 

 make a point of testing these conclusions by 

 fresh observations made in the field from the 

 author's point of view. This is written in no 

 spirit of doubt, for Mr. Thayer's statements 

 and illustrations are, -with certain exceptions, to be 

 considered later, most convincing. No naturalist could 

 reasonably doubt, for example, the significance of the 

 grass-pattern shown in Figf. 7, which the author 

 justly describes as "one of the most remarkable photo- 

 NO. 2139, VOL. 84] 



graphs ever taken of obliteratively coloured birds in 

 nature " (p. 46). The two points by which the bird 

 is most easily recognised are the dark eye and the 

 dark shadow under the feathers, so that tnis wonder- 

 ful illustration helps us to understand the importance 

 of eye-masking markings (see pp. 81, 

 82), as well as of obliterative counter- 

 shading. 



The coloured plates of the " Male 

 Ruffed Grouse in the forest" (II.), the 

 "Cottontail Rabbit" (VTl.), and the 

 "Copperhead Snake on dead leaves" 

 (XI.) are very remarkable illustrations, 

 justly claimed by the author and his 

 father to be " the first ever published, 

 which rightly illustrate and in some 

 respects do justice to the wonderful 

 effects of obliterative coloration, based 

 on the great law of obliterative shad- 

 ing" (p. 128). 



The five coloured plates of cater- 

 pillars (XII. -XYI.) are extremely 

 beautiful, showing for the first time 

 the important part played by oblitera- 

 tive shading in these forms. The 

 attitudes of caterpillars generally must 

 be re-e.xamined in the light now 

 thrown upon them by this great 

 artist-naturalist; for there is little 

 doubt that many of the best-known 

 and commonest illustrations represent 

 an inaccurate position. It is unfor- 

 tunate that the names of so few of the 

 figured species were ascertained, but 

 there should be little difficulty in the 

 identification of such beautiful repro- 

 ductions. There is an evident inadvertence in the 

 orientation of Fig. C or D on plate XII., both repre- 

 sented in a similar position, although D is described 

 as the reverse of C. 



by 



Fig. 4.— Model 



to that shown in Fig, 3, 

 ongly lighted and iherefori 



similarly patterned, but 

 ispicuous. 



The necessities of space prevent a further account of 

 this remarkable and splendidly illustrated exposition 

 of the principles of obliterative colouring, and its dis- 

 tribution throughout the animal kingdom. We must 

 now, in the concluding paragraphs, deal with special 



