546 



SCIENTIFIC NEWS. 



[Nov. 30, 1 883. 



The cuticle is translucent, quite as translucent as the 

 plates of horn used as the windows of old-fashioned 

 lanthorns. The blush of the cutis is visible through it. 

 A multitude of other facts besides those stated above 

 might be cited to show that the tissue of nerves and 

 blood-vessels constituting the cutis is painfully sensitive to 

 the action of light exceeding a moderate degree of intensity. 



Our most advanced physiologists now regard vision as 

 a specialised skin function that has been gradually de- 

 veloped and concentrated in the organs of sight ; that the 

 optic nerve which now sees has been evolved from skin 

 nerves that originally could only feel. This conclusion 

 has been reached by observations on animals which dis- 

 play by comparison a gradual process from localised 

 skin-vision to rudimentary eyes, and onwards to fully 

 differentiated optical apparatus. 



Earthworms, for example, as proved by Darwin, 

 although without eyes, distinguish readily between light 

 and darkness, and this power is only possessed by the 

 anterior portion of the animal. Examples of the progress 

 from this to the rudimentary eyes of the medusa, star- 

 fishes, etc., are quoted in Surgeon-Major Alcock's paper. 



The carbonaceous colouring-matter of the negro is 

 situated in what Malpighi called the rete macosum, or 

 mucous net- work, which constitutes the inner basis of the 

 cuticle or epidermis where the horny cells of the cuticle 

 are formed. This is just where such opaque matter is 

 required for protecting the sensitive nerve-endings of the 

 true skin from the injurious action of excessive sun-glare. 



The position and known functions of the iris appear to 

 me to present another argument in support of this 

 theory. At the back of the eye, in a position correspond- 

 ing to that of thetrueor under-skin,we havea similarmem- 

 brane, similarly including a tissue of outspread nerve-end- 

 ings, those of the specialised optic nerve. In front of this 

 we have the cornea, corresponding to the cuticle, between 

 them the iris. The work performed by the iris is that 

 of a dark, adjustable screen, which admits the quantity ot 

 light demanded for the purposes of vision, but excludes 

 any excess that would produce painful and mischievous 

 nervous irritation. The colour of the iris varies, like that 

 of the skin, with the original habitat of the races of men. 

 The tropical races have dark eyes as well as dark skin. 

 Those of higher latitudes have light eyes and skin. 



This variation proceeds regularly up to a certain lati- 

 tude, and then comes a remarkable and very suggestive 

 exception. The arctic races, the Esquimaux, the Lapps, 

 or Finns, and the " Hyperborean," or Mongolian races 

 generally have dark eyes, " are olivaceous in colour, the 

 skin varying from a kind of sallow lemon peel through 

 various shades of greater depth, but is never entirely 

 fair nor intensely swarthy " (Colonel Chas. Hamilton 

 Smith, " The Natural History of the Human Species"). 



Why this exception ? My answer to this question is 

 that it fits these people to endure the snow-glare to which 

 they are exposed during more than the first half of their 

 long summer daylight. 



They have migrated very widely even to sub-tropical 

 and tropical regions, and there they have more or less 

 dispensed with clothing and have readily developed a 

 darker skin. The Papuans and black Kalmucs are 

 examples of this. 



Canals of Mars. — An American exchange states that 

 Professor Pickering, of the Harvard College Observatory, 

 regards the so-called " canals " of Mars as areas of vege- 

 tation—possibly immense cultivated tracks. 



ROMAN REMAINS AT LLANTWIT- 

 MAJOR. 



{Continued from p. 502.) 



T)ERHAPS the discovery of most general interest is 

 -L the room numbered 14 on the plan. Its interior 

 measurement is 27 ft. by 2c ft.; its walls, standing at 

 present some 2 ft. 6 ins. to 3 ft., are covered with plaster, 

 which in earlier periods of splendour evidently had a very 

 carefully prepared surface, with a graceful and artistic 

 floral design painted in beautiful and varied colours, 

 In course of time this plastering appears to have been 

 injured, and in a subsequent period of less splendour 

 the walls of this room had been re-plastered, the 

 renewed surface being coarse, greyish blue in colour 



Fig. 6.— Wall Decoration. 



with a splash ornament of red and dark blue. In fig. 6 

 a patch of the more recent plastering, with the splash 

 decoration, is shown to the right and shaded diagonally, 

 whilst the other part represents a place where this 

 coarser plastering has fallen off and exposed the 

 superior and more ornamental but injured under sur- 

 face. In this the ground is deep ochre yellow, the con- 

 ventional floral design is red, the central spike having 

 a black outline ; the lower bands are respectively 

 orange, yellow, and red, whilst the dividing lines between 

 them are black and white, the lines at the top being 

 also black and white, enclosing an orange and yellow 

 band, separated by a white line. The spots on the 

 dado are red and white, the ground being pink. 

 The irregular patches are injuries which the plaster has 

 sustained. It is noteworthy that the colours are bril- 



