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KNOWLEDGE & SCIENTIFIC NEWS. 



2/5 



spotted livery, and tliis to a uniform cohiration. In 

 the nestlings of the Emu, Cassowary, and Grebe, for 

 example, the striped dress gives place to one without 

 markings, and this again to a pafternless plumage in 

 the adult stage. The Game-birds furnish us with two : 

 very interesting stages of de\elopment. In some, e.g., 

 Quails, the young arc striped ; the first |)ennaceous 

 plumage — as distinct from the downy plumage — may 

 be described as a brown or buff colour relieved by vari- 

 ous shades of darker brown arranged in the form of 

 streaks, spots, and bars. The adult plumage for both 

 sexes is similar. In others, e.g., many Pheasants, the 

 striped downy plumage is succeeded by a dress re- 

 sembling the immature and adult dress of the Quails. 

 This dress is retained by the female, but in the male is 

 succeeded by a more or less resplendent livery. In 

 other Pheasants, e.g., l%ared Pheasants (C rosso f^lil on), 

 the speckled dress of immaturity is discarded by both 

 sexes for one of more or less brilliancy. 



The same order of coloration, which obtains in the 

 life of the individual in one group, is found in another 

 group only in studying the history of the race. This 

 may appear to be only another way of saying that the 

 history of the species is a recapitulation of the history 

 of the race. Rut in the present connection, it is to be 

 noted, the most primitive species passes through all the 

 possible phases in the course of its growth, while the 

 " race " to which we have referred is of comparatively 

 recent origin — the Limicoljp to wit. Herein we find 

 striped forms like the Redshank, or the Snipe, mottled 

 forms like the Gulls and Terns and some Plovers, and 

 unicoloured dusky forms like the -Skuas and iXlcida?, 

 e.g.. Guillemots. In the Terns and Gulls the mottled 

 nestling gives place to a brown first plumage, which is 

 succeeded by a more or less unicoloured adult dress 

 worn by both sexes alike. 



Longitudinal markings occur but rarely among 

 adult birds. Instances thereof are seen in the Snipe, 

 .-\vocet, Black-throated Di\er, Herons, and Hitterns. 

 N'ow it is worthy of note that in the Snipe and the 

 Bitterns, at least, these peculiar markings are known 

 to be used for protective purposes. The Bitterns when 

 desiring to conceal themselves adopt a perfectly verti- 

 cal position, throwing the head and neck upwards and 

 holding the body perfectly still so that the dark lines 

 down the neck harmonise with the dark inter-spaces 

 between the reeds which form its cover. The Snipe 

 reverses this position, holding the head downwards 

 and presenting the longitudinally-marked back so that 

 the tail points directly up\\ards. 



From the .'Etiological side it must be admitted we 

 have much yet to learn in the matter of these stripes. 

 Where both nestling and adult wear a protective 

 plumage, it seems strange that in many cases a distinct 

 livery should be necessary for each stage. But this 

 may be due to the fact that the environment of the 

 nestling is quite different to the normal environment of 

 the adult. The downy young Ringed Plover, for ex- 

 ample (JEgialitis hiaiiadd), is almost white with dark 

 mottlings ; the adult is buff-coloured above, white 

 below, and barred across the head and breast with 

 black. These bars are apparently protective devices, 

 for while the kahki-coloured body is invisible, the dark 

 bars are conspicuous, but they bear a curious re- 

 semblance to mussels, the empty shells of which occur 

 on every tide-wash, where these birds commonly feetl. 

 But there is no need to expect a very close connection 

 between the two stages in the life-history, for while in 

 many cases tiie stripes of the downy plumage may well 

 be ancestral, and, therefore, of extreme antiquity, the 



plumage of the species is necessarily of more recent 

 origin, and is determined by the re(|uirenients of the 

 environment amid which it has t!e\ eloped. 



Finally, wc are brought to tlie question of llie origin 

 of the stripes. Their remarkably wide-spread 

 occurrence among vertebrates suggests that they must 

 be due in the first place to some deep-seated 

 physiological activities, which determined the de- 

 position of pigment in certain delinite areas, serving 

 either as centres of distribution or as screens for the 

 protection of sensitive regions Irom excessive light. 

 The reasonableness of this latter view is supported by 

 the fact that these stripes occur with striking frequency 

 in " larval " forms, such as of fish and tailed 

 .Amphibia, where the bands of pigment over-run the 

 brain, spinal cord, and lateral line organs. Their 

 occurrence in higher vertebrates would seem to 

 decidedly weaken this hypothesis ; but it may be that 

 the ancient fashion of laying down pigment is for some 

 reason or other adhered to in these groups, just as 

 gill arches, no longer useful, are also de\el()ped. 



It seems hardly likely that these stripes in the case 

 of the birds have been independently acquired, and 

 acquired afresh, too, in each group, at least, in which 

 they occur, solely in response to the need for a protec- 

 tive livery of this particular type. But the adoption 

 of this livery as a method of salvation ready to h.-md 

 seems probable enough. 



The existence of whole-coloured forms seems to ha\e 

 been due cither (a) to the suppression of the stripes in 

 favour of a \et more protective dusky livery, as in the 

 case of the voung W'aterhen (p. 274), where they are 

 just traceable, or of the grizzled covering of the young 

 Ostrich — which retains the original neck-stripes lost 

 in the Cassowary and Rhea — or f;3) to the suppression 

 of pigment to secure a white covering, as in the case 

 of birds which, being nidicolous, lie helplessly exposed 

 in open nests to the glare of the noonday sun, and 

 thereby derive benefit from a white covering. That 

 there is some probability in this suggestion is shown 

 by the fact that the Common Buzzard has contracted 

 a habit of erecting a shelter of green boughs above its 

 nest, replacing these as soon as the leaves wither. 



The question is full of interest, and demands further 

 study. 



REVIEWS OF BOOKS. 



Scientific Pact and Metaphysical Reality. — It has lately been 

 remarked that in tho disturbance of cxistinf; theories which 

 has been produced by the determination of new facts in 

 physical science, there .are few hypotheses which seem totally 

 unworthy of consideration, and few speculations that are, not 

 valid. One mif,'ht note as an accompanyinj.; phenomenon, that 

 the scientific world seems to have been stirred at the same 

 time by a desire to investigate, not the relations of matter and 

 energy alone, but of mind and energy, and to formulate in as 

 ex.act a manner as its knowledge will allow the relation of 

 mankind to its own fate and destiny. Some such design is 

 apparent in both of two books, of widely different seojic, 

 which are before us — " Scientific Fact and Jfctaphysical 

 Reality," by Robert Brandon Arnold (Macmillan), and " Ideals 

 of Science and Faith" (George Allen) in which the Rev. J. I'". 

 Hand collects the essays of writers who approach the problems 

 of man's life or immortality from such widely diflVrent stand- 

 points as those that we expect to be assured by a physicist 

 like Sir Oliver Fodee, a biologist like Professor J. Arthur 

 Thomson, a psychologist such as Professor Muirhead, or 

 educationists, theologians, or divines like Professor Geddes, 

 the Rev. John Kelman, the Rev. Ronald Bayne, or Mr. Wilfrid 

 Ward. The value of such opinions, and of such an assem- 



