when it amounted to 15,000,000l. sterling, since which period the production of California has steadily declined, and the present annual return of the precious metal does not much exceed 5,300,0007.

The total value of the gold produced in the state, from the time of the discovery of that metal in 1848 to the close of 1866, is estimated at 167,260,0007.

III. ON THE COLOUR-PATTERNS OF BUTTERFLIES. By Rev. H. H. HIGGINS, M.A.

THE petals of flowers, the plumage of birds, the surfaces of shells, the hides of quadrupeds, the integuments of polyps, and the wings of insects, are some of the chief objects distinguished by a great variety of natural colour-patterns.

All that I propose to attempt in the present instance is to offer a few remarks on the proximate origin and general configuration of the patches, bands, and spots of colour which adorn the wings of the Rhopalocera.

By the use of the term "proximate origin," the inquiry is limited to the appliances immediately engaged in producing the results under consideration; an inquiry which cannot conveniently be separated from the question, whether amidst the apparently capricious and endless varieties of colour-patterns on the wings of butterflies, may be recognized the elements of a prevailing arrangement.

An example of the kind of agency contemplated may be found in the serrated edge of the leaf of a Potentilla, which, it is said, is the result of a certain configuration of organs discernible in the leaf-bud; or, again, the spines on the shell of a Murex, which may be shown to be the result of tentacular appendages periodically developed in the mollusc.

The physical conditions which have preceded so delicate a result as the shading of the colours on the wing of a butterfly, require a kind of investigation which must be attended with corresponding difficulties. But it will be admitted that in no case is a spot or a band added or obliterated except through the instrumentality of antecedents sufficient to produce the result in question. How far these antecedents are capable of being investigated has yet to be determined.

The rudiments of wings, according to Burmeister, may be observed when the caterpillar has completed its third moulting and has attained its full size. They at first present themselves as short viscous leaves, the substance of which greatly resembles that

of the mucous tunic, and to which many delicate trachea pass which distribute themselves throughout them."

The wings in an imperfect condition, whilst still enclosed by the shell of the chrysalis, are closely folded together with many plications. Can any clue to the subsequent arrangement of the colours be found in the manner in which the wings are folded in the pupa state? If a scrawl of any kind be made on paper with a pen, and if the paper be folded, the ink being inside and still wet, a symmetrical pattern is produced, the sides of which, like the markings on the wings of a butterfly, exactly correspond. And it is manifest that under certain conditions of folding, colouring matter of any kind might, by a comparatively simple process of arrangement, produce patterns remarkable for symmetry and regularity.

In the limited number of instances in which I have been able to examine the sufficiently advanced chrysalis of a butterfly, nothing of this kind has been indicated: the like spots on the right and left wings do not, in the pupa state, coincide; the folds do not bisect the markings; that which becomes a beautifully formed band, begins as a mere line, or a shapeless spot; and this stage of the metamorphosis, if watched, conveys a decided impression that the resulting colour-pattern is not dependent on the folding of the wings in the immature condition.

The perfect wing of a Lepidopterous insect consists of a delicate double membrane, traversed between the folds by nerves or veins ramifying from the base. The wings are covered with minute scales of various shapes and colours, which, in combination, form a pattern much after the manner of the materials used by an artist in constructing a piece of mosaic work.

Three elements then are essential to the wing, the double membrane, the veins, and the scales covering both.

The simplest type of colour presents itself in the plain uniform tint, exhibited when the scales are all exactly alike. Examples of this are rare in nature. A variety of Pieris rape is almost wholly white; Gonepteryx rhamni is almost wholly yellow.

It seems probable, however, that the scales growing on the membrane upon or near the veins would be distinguished from the scales growing on other parts of the membrane by a freer development of pigmentary matter, and that in this manner would arise a kind of primary or fundamental pattern, namely, a pale ground with darker linear markings following the course of the veins, e. g. Pieris crategi.

For the present we shall notice only the upper surface of the wings, in which the prevalence of the primary pattern is more clearly indicated.

Most butterflies exhibit some traces of the black-veined white pattern; and the pattern itself, with slight modifications, is found

in species belonging to eight of the fourteen families into which the butterflies are divided.* (See Plate.)

The fundamental character of this dark-veined pattern is confirmed by the closeness of the gradations connecting it with others apparently altogether distinct. For example, Pieris brassica, and some other insects of the same family, which are wholly white with the exception of a broad black tip at the apex of the fore-wing. Now several exotic species of Pieris present the dark veins expanded at the outer margin of the fore-wing into a deeply scalloped black border; others show the gradual fading of the lower portions of the border, together with attenuation of the venous markings in the disc of the wing, till the passage from the pattern of P. crategi to that of P. brassica is made by almost imperceptible steps.

In the genus Hestia, the primary pattern is diversified by a great variety of black spots and blotches, which are all evidently dependent on the venation: the spots occupy a central position between the veins, or they are bisected by a false vein, or they are in pairs contiguous to a vein. In one fine species there is a broad, black band across the wing; but here (as in almost every other instance) the outlines of the black markings are strongly affected by the veins. We shall see, presently, that this is not the case with the brighter colours; but the black markings are very generally thrown nearer to or farther from the base by the passage of a vein, as geological strata are disturbed by the occurrence of a fault. Even where, as in Euplæa Treitschkei, only a small spot or two of white is shown on the wings, it is pretty plain that the ground-colour of the wings is white, almost wholly obscured by a greater development of the dark scales belonging to the veins.

The scalloped border has been referred to; and as the scalloped band, nearer to or farther from the margin of the wing, is one of the most prevalent kinds of markings, it may be well to see how readily it may arise from the primary pattern. Let it be supposed that at a given distance from the base a portion of the dark scales begin to diverge on each side from the veins. The dark lines thus formed will meet in the middle of the areas between the veins, producing a band of scallops having their concavities towards the base of the wing. If the divergence takes place towards the base, scallops are formed having their convexities in the same direction. If the latter mode of divergence be quickly followed by the former, a row of annular markings between the veins is the result. In this manner may be obtained the simplest and most elementary form of the annular or ocellate spot, which in the higher stages of development becomes distinguished for its variety and exquisite beauty. Of this, more hereafter.

Even in the less likely families, Nymphalidæ and Satyridæ, it occurs in Penthema Lisarda, Orinoma Damaris, and other species.