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to upset the dormant condition-allows the failing growth to continue. The seed swells, the fruit ripens, and a new plant is shed forth upon the earth, the product of two distinct prior individuals.

But if the embryo is not thus quickened, growth in it ceases altogether. The seed shrivels up, the pod does not swell, and no new plant is produced at all. It does not contain within itself the needful energy for further development. Supposing all the flowers on a pea-plant were thus to fail-supposing no pollen were ever to be carried from blossom to blossom-then that particular plant would wither and die out altogether, leaving no offspring at all behind to represent it.

In the case we have supposed, however, the flower did get fertilized, and the pea before me a dormant but still a living plant -is the irrefragable proof that it actually did so. Now, in some instances, perhaps in this one, a flower gets fertilized with its own pollen. In such cases, as a rule, the fruit nevertheless swells out properly and the seed produces a young plant. How, then, are we to reconcile this apparent discrepancy with the general principles of sexual growth laid down above? Well, we must recollect that in a certain sense each leaf is a distinct individual. Again, from the biological point of view the flower consists of modified leaves, some of them specialized to do duty as sepals, some as petals, some as stamens, and some as ovaries. Each of these is therefore in some sense an individual. In the entire community or compound organism, in other words, we may regard the stamens and ovaries as particular members, told off, like the queen-bees and drones in the hive, to fulfill the part of fathers and mothers, while the true leaves, like the workers, provide the food or material for growth. Thus, even in the same flower the stamens and

aries are properly to be regarded as distinct individuals, capable of producing healthy offspring with one another, like the queenbees and drones of the same hive.

Nature, however, does not stop here. The fundamental fact at the bottom of all fertilization whatsoever seems to be this, that where individual formative power fails it can be supplemented and set on foot again by an access of fresh formative power from without. Union is strength: what one can not do, two can. But the fresh fillip seems to be most distinctly felt when it comes not from another member of the same original colony-that is to say, from a stamen of the same blossom or of another blossom on the same plant-but from a totally distinct and separate colony, or, in other words and in more familiar language, from the flower on another neighboring plant. Where the parents are too closely related, it would seem, both are apt to have the same weak points, which therefore reappear in the offspring and vitiate it. But

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deeper down even than that, since both belong to the same colony at the same period of failing growth, the impulse to fresh effort afforded by such a union would appear to be less; indeed, in some cases it is quite inoperative; whereas, when each comes from a separate plant, not only are the chances of diversity in constitution greater, but the constitutional fillip or stimulus to growth is more distinctly marked. Birth is a result of the union of unlike

nesses.

Hence, while among the lowest and least developed flowers self-fertilization (or, to speak more correctly, fertilization of each ovary by its brother-stamens) is very common, among the higher and more specially adapted plants devices for promoting crossfertilization, either by wind or insects, are almost universal. In some instances, indeed, the ovary can not be impregnated by pollen coming from the same flower-the fillip does not seem sufficient to promote growth, and the ovary touched only with pollen of a neighboring stamen remains to the end perfectly sterile. Truly distinct pollen is needed to quicken it. In other cases, though such incapacity does not exist, special arrangements have been made to prevent self-fertilization-the stamens and pistils do not mature together, or else they are so arranged in the blossom that contact of the pollen with the stigma is almost impossible. And in some of the very highest plants of all, the stamen-bearing and ovary-bearing flowers are distributed on totally distinct trees or bushes, thus affording the most perfect known development of the sexual principle-a sort of automatic compulsory exogamy, whereby each blossom must needs intermarry with a member of an entirely different colony.

For the same reason it will now, I hope, at once be clear why the offspring in every case resembles on the whole both parents equally. The various leaves which each rose-tree puts forth are exactly alike, and we don't expect them to be at all otherwise, because they are all similar products of the self-same active and formative energy. However much we may subdivide the parts of a plant, we look forward to finding its manifestations remain unchanged, as in the familiar case of cuttings, grafts, layers, suckers, bulbs, and runners. The different leaves, made of the same ultimate stuff, the new material of the species, resemble one another exactly as two parts of the same lump of clay or putty have similar characters; or exactly as the two halves of the same crystal rebuild their lost parts and renew their original shape alike when immersed in a mass of the same mother-liquid. So, too, we may well believe the undeveloped embryo or unfertilized seed potentially resembles in all things (as far as it goes) the mother-plant; but, as soon as it is fertilized by the pollen from its neighbor, it becomes in every portion of itself part and parcel of two previous

plants; or rather, the resulting new organism is the outcome of a compromise, perhaps even of a struggle for mastery, between all the parts or component elements of the two parent plants. Hence, in all species, animal or vegetable alike, the young on the whole tend to resemble both parents equally, but in different modes of combination, which give them each what we call individuality, and so make them really and truly new plants, not mere reissues of either parent form.

When I had written thus far on this present article, I laid down my pen for a little rest, and strolled out alone upon the dry African hill-side, a lower shoulder of the Atlas range, that stands opposite the villa whence I date these words. By a curious coincidence, as I rambled through the lentisk scrub, I happened to light upon a little bed of natural hybrid orchids, which so admirably illustrate the nature of this peculiar intermixture that I joyfully accepted them to point the moral with which I must close this long lay sermon. Numbers of a large and handsome yellow orchid grow on the slopes of that particular hill, and in and out among them spring members of another yet closely related species, dingier brown, and different in shape, disposition of parts, and general appearance. Some wandering bee, visiting a flower of the yellow orchid at this spot where I stood, had carried away on his head its gummy pollen-masses, and then, contrary to the common habit of bees (who generally visit only one particular species of plant at a time), had deposited them on the stigma of a neighboring brown specimen. I suppose he was a young and inexperienced insect, who had not yet learned to avoid the bad practice of mixing his honeys. From this chance fertilization any number of hybrids had taken their rise, all of them more or less resembling in certain respects both parents. In most cases they had, to a great extent, the distinctive shapes of the brown kind, with a preponderating amount of yellow color. But among them all they presented every possible intermediate type between the two parent forms. It seemed to me that this accidental find exactly fitted in with the subject of my paper. We see here how each embryo seed, separately impregnated by a pollen-grain from another plant, grows out with a tendency to reproduce both ancestral forms equally, and how the conflict between the two tendencies, both of which can not fully be realized, produces in the end an individual compromise-a something which is not quite either, but which combines in varying and incalculable degrees the strongest points of both.

Unless I mistake, we have here the solution (suggested in the main by Mr. Herbert Spencer) for one of the deepest and most fundamental problems of all life, animal or vegetable-the problem of reproduction, heredity, and individual variation.

for its own growth, it gives rise to buds, which become parasitic hydras like itself, and remain attached to it and share all its advantages. The budding continues until a complicated colony of long proboscides, bodies, and tentacles is formed. A young colony of these larvæ is shown in Fig. 12, and an older one in Fig. 13.

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d.

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FIG. 11.-Outline of a Turritopsis, with parasitic Cunian larvæ, copied from McCrady.

The hydra larva of the Liriope is only a short transitional stage in the youth of the adult animal, but in Cunina the larval life has become vastly more important; and this is clearly due to the fact that it has found a home which is extremely favorable to it as a larva, an environment where all its wants are supplied, and where it enjoys so many advantages that the speedy acquisition of the wandering life and high organization of the adult is no longer desirable.

To all ordinary animals the period of infancy is full of danger. Young animals are encompassed on every side by peril from enemies, diseases, and accidents, and the prospect of long life increases enormously as childhood passes and maturity approaches.

Short infancy and rapid development are therefore, in ordinary cases, the conditions which are most favorable for the perpetuation of the species and the welfare of the individual: but this does not hold good of Cunina. The hydra stage has therefore been prolonged, and the larva has acquired the power to produce other larvæ to share its advantages. After a time, however, a flange or collar grows out from the body of each hydra, among the bases of

the tentacles, as shown at e in Fig. 13; and, folding down toward the mouth, gives rise to a swim-bell and bell-cavity. The larva is then set free, and it escapes into the water as a young jelly-fish (Fig. 14), with an enormous proboscis (d), a relic of its parasitic

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FIG. 12.-A colony of three young parasitic larvæ of Cunina.

FIG. 13.-An older colony, consisting of six Hydras, some of which have begun to become transformed into Medusse.

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