More difficult to explain is the laughter excited by scenes or narrations which we call ludicrous, funny, grotesque, comic; and still more so the derisive and contemptuous laugh. Caricature or burlesque of well known men is a favourite method of producing laughter among savages as well as civilised peoples. Why do we laugh when a man on the stage searches everywhere for his hat, which is all the time on his head? Why do we laugh when a pompous gentleman slips on a piece of orange-peel and falls to the ground, or when one buffoon unexpectedly hits another on the head, and, before he has time to recover, with equal unexpectedness hooks his legs with a stick and brings him heavily to the ground? Why did we laugh at the adventures of Mr. Penley in "Charley's Aunt"? In all of these "ludicrous" affairs there is an element of surprise, a slight shock which puts us off our mental balance, and the subsequent laughter, when we realise either that no serious harm has been done or that the whole thing is make-believe, seems to partake of the character of the "laugh of escape." It is caused by a sense of relief when we recognise that the disaster is not real. We laugh at the "unreal" when we should be filled with horror and grief were we assured that there was real pain and cruelty going on in front of us. The laughter caused by grotesque mimicry or caricature of pompous or solemn individuals seems to arise from the same (more or less unconscious) working of the mind as that caused by some unexpected neglect of those social "taboos" or laws of behaviour which we call modesty, decency, and propriety. They either cause indignation and resentment in the onlooker at the neglect of respect for the taboo, or, on the contrary, the natural man, long oppressed by pomposity or by the fetters of propriety imposed by society, suddenly feels a joyous sense of escape from his bonds, and bursts into laughter—the laughter of a return to vitality and nature—which is enormously encouraged and developed into "roars of merriment" by the sympathy of others around him who are experiencing the same emotion and expressing it in the same way.
The laugh of derision and contempt and the laugh of exultation and triumph are of a different character. I cannot now discuss them further than to say that they are either genuine or pretended assertions of joy in one's own superior vitality or other superiority. The "sardonic smile" and "sardonic laughter" have been supposed by some learned men to refer to the smiles of the ancient Sardinians when stoning their aged parents. But they have no more to do with Sardinians than they have with sardines or sardonyx. The word "sardonic" is related to a Greek word which means "to snarl," and a sardonic grin is merely a snarl. In it the teeth are shown with malicious intent, and not as they are in the benevolent appeal of true laughter. Mrs. Grote, the wife of the great historian (who was herself declared by a French wit to furnish the explanation of the word "grotesque"), wrote of "Owen's sugar-of-lead smile"—referring to the great naturalist, Richard Owen. There was no malice in the description, for he had, as some others have, a very sweet smile, accompanied by a strangely grave and disapproving glare in his large blue prominent eyes. It was only apparently sugar of lead; really, it was sugar of milk—the milk of human kindness. The smile of the lost picture called "La Gioconda" is by fanciful people regarded as something very wonderful. It is really the clever portraiture of the habitual "leer" of a somewhat wearied sensual woman. It had a fascination for the great Leonardo, but no profound significance.
CHAPTER XIII
FATHERLESS FROGS
One of the most interesting discoveries of recent date in regard to the processes which go on in that all-important material—protoplasm—which is the physical basis of life and the essential constituent of "cells"—those minute corpuscles of which all living bodies are built—was made in 1910 by a French naturalist, M. Bataillon, and has been examined and confirmed by another French biologist, M. Henneguy. To explain this discovery, a few words as to well-known facts are necessary. It is well known that if we isolate a female frog at the egg-laying season and let her swim in perfectly pure filtered water, and proceed to deposit some of her eggs in that water, the eggs will not germinate; they remain unchanged for a time and then decompose—become, in fact, "rotten." It is a matter of common knowledge that it is necessary for the eggs to be "fertilised" in order that they may start on that series of changes and growth which we call "development," and become tadpoles and eventually young frogs. The "fertilisation" of the frog's eggs is effected in ordinary conditions by the presence in the water of the pond, into which the female sheds them, of microscopic sperm-filaments (often called spermatozoa, or simply "sperms") which are shed into the water at the same time by the male frog.
The egg (the blackish-brown spherical body, as big as a rape-seed, which is imbedded in a thin jelly, and is familiar to those who are drawn by curiosity to look into the waters of wayside ponds in spring) is a single cell or corpuscle of protoplasm distended with dark-coloured and other granules of nutrient substance. A single sperm (though requiring the microscope to render it visible) is also a single cell. It is a minute oval body, with a long serpentine tail of actively undulating protoplasm. Hundreds of thousands of these are shed into the water at the breeding season by the male frog. One is enough to fertilise the egg. The sperm-cells swim in the water, and are chemically attracted by the eggs. As there are so many sperms, one of them is sure to reach each black egg-sphere. It drives its way into the substance of the egg, making a minute hole in its surface; then the protoplasm of the sperm fuses with the protoplasm of the egg, and becomes intimately mixed with it. The egg-cell has a "nucleus," that dense, peculiar, deep-lying, and well-marked "kernel" of its protoplasm which all cells have. It is of essential importance in the life and activity of the cell. The sperm-cell has also a "nucleus," and now (as has been carefully ascertained) the nucleus of the sperm and the nucleus of the egg-cell unite and form one single nucleus. The egg is thereupon said to be "fertilised"—that is to say, "rendered fertile." It at once commences to move. Its surface ripples and contracts and nips in deeply, so that the sphere is marked out into two hemispheres. These are two "cells," or masses of protoplasm, adhering to each other. Each is provided with its own distinct nucleus or cell-kernel, for the first step in the division of the egg-sphere is the division within it of its newly constituted nucleus into two, each half consisting of nearly equal proportions of the mingled substance of the sperm-nucleus and the egg-nucleus. The two first cells or hemispheres again divide, and so the process goes on until the little black egg has the appearance of a mulberry, each granule of the berry being a cell provided with its own nucleus derived from the original nucleus formed by the fusion of the nuclei of the paternal and maternal cells. In the course of a day or two the division has proceeded so far that the resulting "cells" are so small as to be invisible with a hand-glass, and require one to use a high magnifying power in order to distinguish them. And there are hundreds of them; the whole mass of the "egg" within, as well as on the surface, has divided into separate cells. They go on multiplying, take up water, and nourish themselves on the granular nutritive matter present from the first in the egg-cell. The little mass elongates, increases in size, and gradually assumes the form of a young tadpole.
We see, then that the process of fertilisation consists in two things, the latter of which necessitates the former, viz. in the breaking or penetration of the surface of the egg-cell by the active sperm filament and second in the fusion of the substance of the sperm filament with that of the egg in such a way that there is a distinct and intimate fusion of the nucleus of the sperm filament with the nucleus of the egg-cell. The recent discovery of M. Bataillon is this, viz. that you can make the frog's egg develop in a perfectly regular way and become a tadpole and then a young frog without the admission to it of a sperm-filament or of any substance derived from the male frog. All you have to do—and the operation, though it sounds easy and simple, is an exceedingly delicate and difficult one—is to prick with a fine needle the surface of the little black egg-sphere (not merely of the jelly surrounding it) when it is shed by the female frog into perfectly pure water free from sperms or anything of the sort. The slight artificial puncture acts as does the natural puncture by the swimming sperm-filament, and is sufficient! The egg proceeds to develop quite regularly. There is no fusion of the nucleus of the egg-cell with any matter from the outside; no paternal "material" is introduced, but the nucleus of the egg-cell divides just as though there had been! The whole progeny of cells, successively formed, are the pure offspring of the maternal egg-cell and its nucleus. The tadpoles and young frogs so produced are examples of what is called "parthenogenesis"—that is to say, virginal reproduction—reproduction without fertilisation by material derived from a male parent! The needle, which gives off no material, but simply makes a tiny break in the surface of the egg, does all that is necessary!
To those not acquainted with all that has been ascertained as to the reproduction of lower animals such as insects, crustaceans, and worms, this discovery will appear more astonishing than it really is. We know of many lower animals in which the egg-cells produced by the females do regularly and naturally develop without the intervention of a male and without fertilisation. In an earlier volume[7] of this "Easy Chair Series" I wrote of this curious subject, and described the virgin reproduction or parthenogenesis of the hop-louse and other plant lice, of some moths, of some fresh-water shrimps, and of the queen bee (who produces only drones by eggs which are not fertilised). But I had to point out then that no case was known of "parthenogenesis"—that is to say, reproduction by unfertilised eggs—among the whole series of vertebrate animals, the fishes, amphibians, reptiles, birds, and mammals. The chief point of novelty in M. Bataillon's discovery is that we have now an experimental demonstration of parthenogenesis in a vertebrate animal, and in one so highly organised as the frog. And equally interesting, indeed more important from the point of view as to the real meaning and nature of fertilisation, is the mode in which the parthenogenesis of the frog is set going, namely, by a mere prick of the surface film of the ripe egg!