74 



HARD Wl CKE ' S S CIE NCE- G OS SI P. 



appear and fade, and in some cases (as in the cuttle- 

 fish) seem to be influenced by the will or nerve-state 

 of (he animal. 



There can be little doubt that the beauteous 

 colouring of animals is occasioned primarily by the 

 presence of a large amount of oxygen in the blood or 

 in the tissues. No doubt can be entertained that 

 this gas lias the property not merely of supporting 

 life, but also of vitalising, animating, and beautifying 

 the living tissues and fluids. Dark and dun venous 

 blood, when infused by oxygen, immediately becomes 

 bright and beautifully scarlet. This red blood 

 suffusing ihe eyes (as in the look of love) <jr the 

 cheeks (as in blushing) imparts to the human face its 

 supreme attractiveness in these its moments of most 

 eminent loveliness. And if we consider for a moment 

 the potent influences in this respect of oxygen among 

 material bodies, then shall we have an earnest of its 

 sway in the case of organic bodies. Most schoolboys 

 are familiar with the experiment of burning a piece 

 of sulphur or phosphorus or iron wire in the gas, 

 and the brilliant and beautiful sight thereby witnessed. 

 Some metals (such as strontium, barium, copper, 

 etc.) have the property of imparting to their salts 

 when ignited tints of red, green, blue, etc. ; but 

 pyrotechnists in their coloured fires, in addition to 

 these, always use nicre or chlorate of potass, which 

 are highly charged with oxygen ; and thereby the 

 beautiful effects of their "stars," etc., are much 

 enhanced. The aspect of fire in itself when not 

 overpowering is pleasurable. Now, what is fire or 

 heat? It is simply an act of rapid chemical union 

 between oxygen and certain bodies called inflam- 

 mables. When an inorganic body is heated the atoms 

 or primary elements which compose its mass are 

 thrown into a state of active motion, and the presence 

 of oxygen around the burning body serves to increase 

 and intensify this internal agitation. A similar effect 

 no doubt occurs in the case of living tissues or 

 organic bodies. The presence of oxygen in the blood 

 increases the motion of its particles, and beautifies 

 their aspect. The presence of oxygen in the tissues, 

 especially the skin or epidermis, vivifies and increases 

 its activity, its decay and repair, the special organic 

 vitality of its molecules, and so-wise heightens its 

 beauty. As the action of this gas beautifies and 

 increases the motion of the ultimate particles of 

 in iterial bodies, so we may presume it beautifies and 

 perfects the primary vital motions of animal tissues. 

 In the former case the oxygen, it would seem, must 

 be generated, or be external to the bodies ; in the 

 latter case, the oxygen would appear to be stored in 

 the organic substance itself. Oxygen (as aforesaid) 

 becomes latent, and is stored up in every one of the 

 animal tissues, in every living bit of protoplasm. In 

 I is manner we shall perhaps be able to account for 

 the wondrous transformation which those lavish con- 

 sumers of oxygen, viz. birds, undergo in the spring- 

 time. It would seem that during the winter the 



oxygen is gradually accumulated in the feathers and 

 skin, and on the approach of spring it bursts into 

 activity, when new feathers are developed, and the 

 exquisite embellishment incident to that season takes 

 place. This magnificent development of animal 

 decoration is connected also with, or at least runs 

 parallel to, the sexual impulse. The vital energy, 

 actuated by the stimulating influence of oxygen, 

 operates among other regions of the body, and stirs 

 other functions as well as those of the skin and its 

 appendages. In most animals the male is more 

 beauteously apparelled than the female, and the 

 former is in the spring-time more sexually perturbed 

 than the latter. So also if we consider instances of 

 animals not so signally decorated as birds, we shall 

 find their comparatively sombre colouring related in 

 some way to their small share of vernal vital energy. 

 Thus the mammalia exhibit grays, black, brown, 

 drab, yellow, fawn colours, but no green, and scarcely 

 any blue or brilliant scarlet ; and their periodical 

 vernal energy is, as exhibited by their sexual pro- 

 pensities, dull and languid as compared with that of 

 birds or fish. A few birds and insects, such as the 

 trogons and some ground-beetles, are dull and silent, 

 yet are they splendidly coloured. In these ex- 

 ceptional cases, however, it may be found that the 

 animal energy, although individually concentrated, is 

 limited in amount, or is drained off by some channel 

 to be utilised in some other department of the animal 

 economy. The great Darwin, viewing, as was his 

 wont, everything from a material or sensuous point 

 of view, was of opinion that active or voluntary 

 sexual selection is one of the chief causes, if not the 

 chief cause, of all the variety and beauty of animal 

 colour. This agency, however, although it may to 

 some extent practically account for the actual beauty 

 of certain individuals at present existing, cannot be 

 considered the fundamental cause thereof. Sexual 

 selection is at best a secondary and, as it were, visible 

 or tangible agency that occasions the primary and 

 recondite cause to operate. 



{To be continued) 



NOTES ON NEW BOOKS. 



f^EOLOGY: Chemical, Physical, and Stratigra- 

 \JT phical, by Joseph Prestwich, M.A., F.R.S., etc. 

 In two volumes : vol. i. Chemical and Physical (Ox- 

 ford, at the Clarendon Press). 



The stony science cannot complain now of the 

 want of advanced text-books. The real difficulty is 

 which to select, for the best and most renowned 

 teachers of modern geology have devoted themselves 

 to writing manuals. No other science is now so well 

 off in this respect. Jukes, Lyell (a new edition of 

 which, by Duncan, we recently noticed), Phillips 

 (edited by Etheridge and Seeley), the two Geikies 



