592 



The Review of Reviews. 



A NEW VIEW OF PROTECTIVE COLOURING. 



Mrs. Arthur Bkll writes in Science Progress for 

 October on Abbott Thayer's discovery of what he 

 considers the basic principle of protective colouration 

 in the animal kingdom. The ordinary assumptions 

 have been natural selection, sexual selection, pro- 

 tective mimicry, and protective concealment. 



THREE PRINCiri.ES OF CONCE.^LMEN' T 



Over against these Abbott Thayer puts his three 

 great principles : — 



With ihe governing purpose of making living forms indis- 

 linguislialile from their normal background, the development ot 

 animal colouration has, according to Thayer, been, so to speak, 

 liirccted by three great principles, which he calls respectively 

 those of "Coiintershading," those of the "Averaging of the 

 background," and those of the " Obliteration of Outline." 



In these three principles lies the key to the whole subject. 

 The principle of Countershading is Thayer's cardinal dis- 

 covery. Though his book is called " Concealing Coloration," 

 it i-. one of his main contentions that "shailingis really more 

 important than colour, because it is primarily an attribute of 

 form, while colour is only secondarily so." " Make the 

 rounded body of a creature look flat, and, however it is 

 coloured, it will lose much of its conspicuousness." It is then 

 for this reason that "animals are painted by Nature darkest in 

 those parts which tend to be most lighted by the sky's light and 

 vice versa." Thayer insists that the fact that the great m.ajority 

 of living species are shaded more heavily on the back and 

 li:;hlly on Ihe belly is evidence of the working of this 

 principle. 



" .WKKAGING OF THE BACKGROUND." 



The principle of averaging of the backgroiuid agaiji gives a 

 new significance to colouration proper. If the illusion of 

 flatness is to have its full effect, the object must be so marked 

 or mottled as to be indistinguishable from its background. 

 Thayer claims that on animals which need the highest degree 

 of inconspicuousness there h.as been developed "a sort of 

 compound picture of their normal background, a picture 

 seemingly made up of the averaging of innumerable back- 

 grounds." 



" OnUTERATION OF OUTLINE." 



But the really protective scheme goes farther still, and defi- 

 nitely aims, so to speak, at merging itself into the background 

 so that the outline of the animal is completely obliterated. It 

 is not enough that the living creature should resemble its 

 inanimate background : it must merge with and fade away into 

 it. Thus a new purpose is found by Thayer for the very daring 

 of those patterns, stripes and colour contrasts, the developing 

 antl fixing of which have so often been traced tosexual selection, 

 or again, in some cases of gregarious species, to their efficacy 

 as warning signs or danger signals to others. The peacock's, 

 tail, according to Thayer, is not exclusively to ple.ase the 

 peahen, or the rabbit's to guide its young or warn its fellows. 

 The object of both is to break up the continuous outline of the 

 ( rcalure's silhouette. 



It is one of his cardinal principles that a scheme of coloura- 

 tion may be at once exceedingly bold and most efftclivc as a 

 disguise. What Thayer does is to extend to a whole variety 

 of similar cases what has long been recognised of the tiger in 

 the iungle : that markings, which against a background of a 

 uniform hue make their possessor exceedingly conspicuous, 

 completely conceal him amiil the varied jungle in which he 

 hunts. Anything which breaks up or cuts into sections the 

 surface of the animal's form makes against the possibility of 

 recognising it as what it is. 



A very attractive feature in the December Pcaison's 

 Magazine deals with this same subject of the protec- 

 tive colouring of animals, and some excellent illustra- 

 tions in colours enrich the article. 



COLOUR IN FOOD. 



Science Progress for October contains an article on 

 the ethics of food. The writer says : — 



The objection that has been taken to bleaching flour would 

 seem to be quite illogical in view of the public demand for 

 sugar coloured blue so as to counteract the yellowness which is 

 characteristic of all but the most highly refined material. 

 Colour, indeed, is an ethical factor of no slight importance 

 in connection with food ; thus milk, and especially butter, 

 are demanded dyed yellow as proof of quality, though every- 

 one is aware that both articles are naturally of a pale hue. 

 Other foods are dyed red before they are placed on the 

 market. 



The writer rejoices that the Local Government 

 Board has disposed of what he calls the " standard 

 bread craze." The conclusions it arrives at on the 

 bleaching of flour are given : — 



(l) That when properly carried out bleaching has no appre- 

 ciable effect on the baking qualities of flour ; 

 ' (2) That bleaching cannot counteract defects in flour due to 

 tmsoundness in the wheat from which it was milled ; 



(3) That the improvement of flour by bleaching represents a 

 pecuniary gain to the miller ; 



(4) That so long as buyers of flour attach importance to 

 whiteness, they are liable when purchasing bleached flour to be 

 supplied with an article different in quality from that which 

 they believe they are receiving. 



Dr. Hamill supports the conclusion that bran is not only 

 itself resistant to digestion, but also has the property of causing 

 other materials eaten at the same time to be less perfectly 

 digested. He is also unable to confirm the supposed .advan- 

 tages entire whealen bread possesses in supplying fluorine to 

 the teeth or in preventing dental caries. 



The writer concludes: — 



The question of bread is mainly an economic one. In the 

 case of an average liberal mixed diet, the advantages which one 

 variety of bread may possess over another become negligible. 

 The extra cost of the proprietary breads more than counter- 

 balances any superiority in nutritive value, far better value 

 being obtained by applying the difference in cost to the purchase 

 of other foods. 



IN PRAISE OF CAUCUS RULE. 



The October number of the Conservative Quarterly 

 Rcviciu, in a paper on Ten Years of the Australian 

 Commonwealth, writes very sympathetically of the 

 influence of the Australian Labour Party, and 

 defends it being ruled by the caucus. The writer 

 says that in the case of a fusion of many diverse 

 tendencies and parties such as compose the Australian 

 Labour Party, caucus rule is the only safe rule. It 

 is the only mechanism in modern politics capable of 

 educating and restraining the wild men of a party. 

 The newcomer soon becomes controllable. Having 

 been allowed to state his case fully, without interruj)- 

 tion, he takes defeat calmly. He listens to the other 

 side, and sometimes is converted by it : — 



Nor is this system, in practice, incompatible with real leader- 

 ship. While Mr. Watson was the Labour leader, the caucu- 

 praclically gave him a free hand; when he was compelled lor 

 private reasons to resign, the few members who had given him 

 some trouble actually off'ered to obstruct no more if only he 

 would withdraw his resignation. It is quite possible that Mr. 

 Kishcr, if he justifies his position by as many years of as good 

 le.adcrship, will enjoy the same confidence. 



