6 



KNOWLEDGE. 



[January 1, 1895. 



these transverse stripes and dark blotches must have 

 originated ch novo cjuite independently in each of the 

 groups in question. Indeed, when we remember that the 

 coloration of both the zebras and the giraffes is generally 

 stated to be of a protective nature — the stripes of the 

 former rendering the animals indsible on sandy ground 

 in moonhght, and to a great extent also in sunlight, while 

 the blotches of the latter harmonize exactly with the 

 checkered shade thrown by the mimosa trees among which 

 they feed — it is incredible that both types should have 

 been evolved, according to a rigid rule, from animals 

 marked by dark longitudinal stripes. 



Another instance of the same nature is afforded by the 

 cats, in most of which the coloration appears to be mainly 

 of a protective nature ; plain-coloured species, like the 

 puma and lion, having tawny coats harmonizing with the 

 sandy deserts which these animals often inhabit, while the 

 vertical stripes of the tiger resemble the perpendicular 

 lights and shadows of a grass jungle. The clouded 

 markings of the marbled cat and clouded leopard assimi- 

 late with the boughs on which these species repose, and 

 the spotted pelage of the Indian desert cat renders the 

 creature almost invisible in stony deserts. To suppose 

 that all such adaptations have been produced in the regular 

 order required by the theory is as incredible as in the last 

 case. There is, moreover, the circumstance that the young 

 of the uniformly-coloured puma are spotted, thus giving 

 an instance of the direct passage from a spotted to a 

 plain-coloured form without the intervention of a trans- 

 versely striped stage : precisely the same thing also 

 occurring in the case of the deer. 



If we look for the most primitive mammals with longi- 

 tudinal dark stripes over the greater part of the upper 

 surface, such types being wanting in the marsupials, we 

 shall find them in the striped mangooses {(iKli(licti,i) of 

 Madagascar, already mentioned. And as the civets and 

 allies are certainly the most generalized of existing 

 carnivora (although that order occupies a somewhat high 

 position), this case tends, in a certain degree, to lend some 

 support to the view that longitudinal dark stripes are an 

 early type. The rarity of animals exhibiting this pattern 

 over all their bodies, coupled with the frequent retention 

 of a longitudinal dorsal stripe, are likewise in some degree 

 confirmatory of the same view. With regard to the con- 

 spicuous black and white stripes on the cheeks of the 

 badger, and throughout the head and body in the skunks. 

 South African weasel, and Cape polecat, it may also be 

 argued, with some show of reason, that we have an old 

 type of coloration. In the ancestors of the badger such a 

 type may have been found too conspicuous, and accordingly 

 have been removed except from the face ; whereas in the 

 other forms, all of which are more or less evil-smelling 

 creatures, a conspicuous coloration is an advantage, as 

 warning off other animals from attacking them in mistake 

 for harmless kinds, and the boldly alternating stripes have 

 accordingly been retained and rendered as conspicuous as 

 possible. 



Did space permit, we might dilate to almost any extent 

 on the subject of spots and stripes ; but sufficient has, we 

 hope, been said to indicate the interest attaching to the 

 coloration of mammals, and to show how far we are from 

 understanding the causes and modes which have brought 

 about the present state of things. That uniformly-coloured 

 mammals form the climax of colour-evolution in the case 

 of stripes and spots may be pretty safely admitted. It may 

 further be considered probable that longitudinal dark stripes 

 are an old type of coloration in at least some groups, 

 although it does not follow that this will hold good for all, 

 the marsupials being possibly an exception. Transverse 



stripes cannot, however, be made to accord with Prof. 

 Elmer's theory, since not only do they exist in some of 

 the most primitive of all mammals, but they reappear in 

 certain specialized groups where there is no evidence of a 

 previous spotted stage having been passed through. While, 

 therefore, far from improbable that there may be a certain 

 substratum of truth in what we may call the " longitudinal- 

 spotted-transverse-uniform " theoryof coloration, we submit 

 that in its present guise it cannot adequately explain the 

 whole evolution of " spots and stripes in mammals." 



SURREY: ITS GEOLOGICAL STRUCTURE. 



By Prof. J. Logan Lobley, F.G.S., &c. 



THE County of Surrey strikingly exemplifies the 

 remarkably diverse geological structure of the 

 British Islands, in which comparatively small area 

 there are represented nearly all the sedimentary 

 rocks of the globe, for in this southern county 

 with an area of only 486,039 acres, or about 760 square 

 miles, no less than a dozen of the recognized geological 

 formations are to be found. These are in ascending order 

 as follows : the Hastings Sands, the Weald Clay, the 

 Lower Greensand, the Gault, the Upper Greensand, the 

 Chalk, the Thanet Sands, the Woolwich Beds, the Old- 

 haven Beds, the London Clay, the Bagshot Sands, 

 Pleistocene Deposits, and Alluvium. 



Surrey also affords an excellent illustration of the intimate 

 connection between surface configuration and geological 

 structure, since the physical divisions of the area are each 

 coincident with the topographical extension of geological 

 formations. These physical divisions, seven in number, 

 are very distinct and will be readily recognized. They are 

 (1) the undulating country lying between the eastern half 

 of the Surrey Downs and the Thames, (2) the Downs area 

 extending east and west through the whole length of the 

 county but of varying breadth, (3) the long vale or 

 succession of vales immediately to the south of the line of 

 Downs called Holmesdale, (4) the western expansion of the 

 southern boundary ridge of the Holmesdale vale, (5) the 

 north-western broad expanse of heath-lands, (6) the plain 

 that forms the southern side of the county, and (7) the 

 south-eastern upland area contiguous to Kent and Sussex. 

 These areas are conspicuously different in surface con- 

 figuration and in soils, in aspect and productions, and have 

 each an entirely different geological structure. 



The last named of. the seven areas, at the south-east of 

 the county, is on the oldest rocks of Surrey, the Hastings 

 Sands, which rise at Dry Hill Camp to 56-1 feet above 

 Ordnance Datum. The beds represented are the Lower 

 and Upper Tunbridge Wells Sands, with the intermediate 

 Grinstead Clay, which, however, has but a small outcrop. 

 The whole area is inconsiderable in extent, but aft'orda 

 from its elevated surface and rich surroundings beautiful 

 scenery. 



The extensive and richly-wooded plain stretching along 

 the Sussex border is the Surrey portion of the great Weald 

 Vale, that extends through Kent eastwards to the sea. It 

 IS whoUy formed by the Weald Clay, which, however, is 

 covered in many places by superficial gravels. In Saxon 

 times this area was covered by a dense forest of oaks, the 

 Forest of Anderida, and even at present the timber is 

 largely oak, which tree flourishes generally on clays. The 

 ancient forest was greatly cleared by the felling of the trees 

 for the production of charcoal, much of which was employed 

 for smelting the ironstone of the Weald, an ore that was 

 largely used for iron previous to the present century. The 

 Weald Clay was estimated by ilr. Topley to have a thickness 



