and the Herschels; in geology, Hutton, Lyell, and the Geikies; in biology, Buffon, Lamarck, the Darwins, Huxley, and Spencer; in psychology, Spencer, Romanes, Sully, and Ribot; in sociology, Spencer, Tylor, Lubbock, and De Mortillet—these have been the chief evolutionary teachers and discoverers. But the use of the word evolution itself, and the establishment of the general evolutionary theory as a system of philosophy applicable to the entire universe, we owe to one man alone—Herbert Spencer. Many other minds—from Galileo and Copernicus, from Kepler and Newton, from Linnæus and Tournefort, from D'Alembert and Diderot, nay, even, in a sense, from Aristotle and Lucretius—had been piling together the vast collection of raw material from which that great and stately superstructure was to be finally edified. But the architect who placed each block in its proper niche, who planned and designed the whole elevation, who planted the building firmly on the rock and poised the coping-stone on the topmost pinnacle, was the author of the 'System of Synthetic Philosophy,' and none other. It is a strange proof of how little people know about their own ideas, that among the thousands who talk glibly every day of evolution, not ten per cent. are probably aware that both word and conception are alike due to the commanding intelligence and vast generalising power of Herbert Spencer.
STRICTLY INCOG.
Among the reefs of rock upon the Australian coast, an explorer's dredge often brings up to the surface some tangled tresses of reddish seaweed, which, when placed for a while in a bucket of water, begin slowly to uncoil themselves as if endowed with animal life, and finally to swim about with a gentle tremulous motion in a mute inquiring way from side to side of the pail that contains them. Looked at closely with an attentive eye, the complex moving mass gradually resolves itself into two parts: one a ruddy seaweed with long streaming fronds; the other, a strangely misshapen and dishevelled pipe-fish, exactly imitating the weed itself in form and colour. When removed from the water, this queer pipe-fish proves in general outline somewhat to resemble the well-known hippocampus or sea-horse of the aquariums, whose dried remains, in a mummified state, form a standing wonder in many tiny domestic museums. But the Australian species, instead of merely mimicking the knight on a chess-board, looks rather like a hippocampus in the most advanced stage of lunacy, with its tail and fins and the appendages of its spines flattened out into long thin streaming filaments, utterly indistinguishable in hue and shape from the fucus round which the creature clings for support with its prehensile tail. Only a rude and shapeless rough draught of a head, vaguely horse-like in contour, and inconspicuously provided with an unobtrusive snout and a pair of very unnoticeable eyes, at all suggests to the most microscopic observer its animal nature. Taken as a whole, nobody could at first sight distinguish it in any way from the waving weed among which it vegetates.
Clearly, this curious Australian cousin of the Mediterranean sea-horses has acquired so marvellous a resemblance to a bit of fucus in order to deceive the eyes of its ever-watchful enemies, and to become indistinguishable from the uneatable weed whose colour and form it so surprisingly imitates. Protective resemblances of the sort are extremely common among the pipe-fish family, and the reason why they should be so is no doubt sufficiently obvious at first sight to any reflecting mind—such, for example, as the intelligent reader's. Pipe-fish, as everybody knows, are far from giddy. They do not swim in the vortex of piscine dissipation. Being mostly small and defenceless creatures, lurking among the marine vegetation of the shoals and reefs, they are usually accustomed to cling for support by their snake-like tails to the stalks or leaves of those submerged forests. The omniscient schoolboy must often have watched in aquariums the habits and manners of the common sea-horses, twisted together by their long thin bodies into one inextricable mass of living matwork, or anchored firmly with a treble serpentine coil to some projecting branch of coralline or of quivering sea-wrack. Bad swimmers by nature, utterly unarmed, and wholly undefended by protective mail, the pipe-fish generally can neither fight nor run away: and therefore they depend entirely for their lives upon their peculiar skulking and lurking habits. Their one mode of defence is not to show themselves; discretion is the better part of their valour; they hide as much as possible among the thickest seaweed, and trust to Providence to escape observation.
Now, with any animals thus constituted, cowards by hereditary predilection, it must necessarily happen that the more brightly coloured or obtrusive individuals will most readily be spotted and most unceremoniously devoured by their sharp-sighted foes, the predatory fishes. On the other hand, just in proportion as any particular pipe-fish happens to display any chance resemblance in colour or appearance to the special seaweed in whose folds it lurks, to that extent will it be likely to escape detection, and to hand on its peculiarities to its future descendants. A long-continued course of the simple process thus roughly described must of necessity result at last in the elimination of all the most conspicuous pipe-fish, and the survival of all those unobtrusive and retiring individuals which in any respect happen to resemble the fucus or coralline among which they dwell. Hence, in many places, various kinds of pipe-fish exhibit an extraordinary amount of imitative likeness to the sargasso or seaweed to whose tags they cling; and in the three most highly developed Australian species the likeness becomes so ridiculously close that it is with difficulty one can persuade oneself one is really and truly looking at a fish, and not at a piece of strangely animated and locomotive fucus.
Of course, the playful pipe-fish is by no means alone in his assumption of so neat and effective a disguise. Protective resemblances of just the same sort as that thus exhibited by this extraordinary little creature are common throughout the whole range of nature; instances are to be found in abundance, not only among beasts, birds, reptiles, and fishes, but even among caterpillars, butterflies, and spiders, of species which preserve the strictest incognito. Everywhere in the world, animals and plants are perpetually masquerading in various assumed characters; and sometimes their make-up is so exceedingly good as to take in for a while not merely the uninstructed ordinary observer, but even the scientific and systematic naturalist.
A few selected instances of such successful masquerading will perhaps best serve to introduce the general principles upon which all animal mimicry ultimately depends. Indeed, naturalists of late years have been largely employed in fishing up examples from the ends of the earth and from the depths of the sea for the elucidation of this very subject. There is a certain butterfly in the islands of the Malay Archipelago (its learned name, if anybody wishes to be formally introduced, is Kallima paralekta) which always rests among dead or dry leaves, and has itself leaf-like wings, all spotted over at intervals with wee speckles to imitate the tiny spots of fungi on the foliage it resembles. The well-known stick and leaf insects from the same rich neighbourhood in like manner exactly mimic the twigs and leaves of the forest among which they lurk: some of them look for all the world like little bits of walking bamboo, while others appear in all varieties of hue, as if opening buds and full-blown leaves and pieces of yellow foliage sprinkled with the tints and moulds of decay had of a sudden raised themselves erect upon six legs, and begun incontinently to perambulate the Malayan woodlands like vegetable Frankensteins in all their glory. The larva of one such deceptive insect, observed in Nicaragua by sharp-eyed Mr. Belt, appeared at first sight like a mere fragment of the moss on which it rested, its body being all prolonged into little thread-like green filaments, precisely imitating the foliage around it. Once more, there are common flies which secure protection for themselves by growing into the counterfeit presentment of wasps or hornets, and so obtaining immunity from the attacks of birds or animals. Many of these curiously mimetic insects are banded with yellow and black in the very image of their stinging originals, and have their tails sharpened, in terrorem, into a pretended sting, to give point and verisimilitude to the deceptive resemblance. More curious still, certain South American butterflies of a perfectly inoffensive and edible family mimic in every spot and line of colour sundry other butterflies of an utterly unrelated and fundamentally dissimilar type, but of so disagreeable a taste as never to be eaten by birds or lizards. The origin of these curious resemblances I shall endeavour to explain (after Messrs. Bates and Wallace) a little farther on: for the present it is enough to observe that the extraordinary resemblances thus produced have often deceived the very elect, and have caused experienced naturalists for a time to stick some deceptive specimen of a fly among the wasps and hornets, or some masquerading cricket