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spaces between the gills will be found to be packed with a granular slimy substance, known to fishermen as "white spat," and disclosed under the microscope of the naturalist as a teeming mass of developing eggs. As development proceeds, the granules become colored, and the fishermen then call them "black spat." Frank Buckland likens the spat in his condition to very fine slatepencil-dust; and he found from experiment that the number of developing eggs in an oyster varies from 276,000 to 829,000. He says:

"One fine hot day the mother-oyster opens her shell, and the young escape from it in a cloud, which may be compared to a puff of smoke from a railway engine on a still morning. Each little oyster is provided at birth with swimming organs, composed of delicate cilia, and by means of these the little rascal begins to play about the moment he leaves his mother's shell."

The "little rascal" in some respects resembles and in other respects differs from its mother. It resembles its mother in having a shell of two valves, but the valves are smooth and transparent as glass; symmetrical, and united by a straight hinge. The mouth, which as yet of course has no mustache, is large and opposite the hinge. There are no gills. The shell is closed by a muscle similar in function to that of the mother, but different in position. But the most noticeable point of difference between the little rascal and its mother is the possession of an oval cushion projecting between the edges of the valves, and bearing on its edges the delicate swimming hairs by which the little embryo mollusk propels itself through the water amid its myriad companions, and enjoys for a while a vigorous and active life. By means of special muscles, the cushion with its swimming-hairs may be withdrawn into the shell, whereupon the oyster sinks.

It is pleasant to think that even the sedate and sedentary native enjoys, if only for a few days, an active, frisky, mischievous boyhood. In this it resembles the vast majority of bivalve mollusks. Our oyster is indeed peculiar in affording any protection to its young. Most bivalves, and even such near relations as the Portuguese oyster and the American oyster, are cast adrift so soon as they are born, and undergo no period of incubation beneath the mantle-wing of the mother. A curious example of a somewhat similar protection is afforded by the fresh-water mussel. The eggs in this case become lodged in the chambers of the outer gills. Here they develop into embryos so unlike the parent that they used to be regarded as parasites. They are minute bivalve shells, with triangular valves. The hinge runs along the base of the triangle, while the apex is curved round into a strong toothed beak. The small fry remain for a long time in the gill of the parent, the neighborhood of fish such as perch or sticklebacks seeming to have some influence in determining their ejection. They then swim by flapping

their valves, and ere long attach themselves, by fine threads with which they are provided, to one of the fish, and hang there, snapping their valves until they bury them in the skin of the fish. Becoming thus enveloped in the skin they there undergo a complete metamorphosis, by which they are converted into tiny mussels which are set free and drop to the bottom. This, in the case of the mussel, is Nature's provision for the preservation of the race. Were the fry hatched as free-swimming embryos, they would inevitably be swept away by the seaward current of the river, and the mussel, as a freshwater race, would be unable to maintain its existence.

The existence of the adult oyster is not altogether free from danger. What with sponges tunneling in their shells, dog-whelks boring neat holes and sucking their sapid juices, and artful starfishes waiting for them to gape, and then inserting insidious fingers, they have rather a lively time of it. But the short active life of the oyster-fry is beset with yet greater dangers. It is a sensitive little thing, and succumbs to the cold of inclement seasons. It is also a tasty little morsel, and is greedily swallowed by any marine monster that has a big enough mouth-for there are epicures in plenty among the marines. And when, tired of the giddy dance of youth, he would fain settle down into sedate and sedentary bearded oysterhood, it is but too probable that the inexorable tides and currents of the very existence of which he, like many another gay youngster, was doubtless ignorant-have swept him out into the deep sea, or to some uncongenial spot, where he is choked so soon as he endeavors to settle.

The settlement of young oysters is spoken of by the fishermen and oysters farmers as a "fall of spat." It is part of the business of oyster-culture to collect the spat, which may then be transferred to some locality especially fitted for the growth and fattening of the young mollusks. For this purpose tiles are employed, covered with a layer of chalk, which is afterward easily removed, together with the young oysters adhering to it. These are placed on the bottom. But they are apt to get covered with slime, or to lose the roughness of their surface, and thus to become unsuitable for the reception of the spat. To obviate this difficulty floating collectors are now in some places employed. These are moored near the surface where the oyster-fry disport themselves before their shells become so thick as to weigh them down. Floating cars or frames containing seedoysters are also sometimes employed with considerable success.

When they first settle, and adhere to the tiles and collectors, or to the gravel, dead-shells, etc., which form the natural collecting medium (or "culch," as it is termed), they are very minute. But they grow rapidly, and in six or eight months attain the size of a threepenny-piece, when they are known as "brood." The diameter

of an oyster at two years is about two inches; another inch is added in the third year; after which the growth is much less rapid. As a rule, the oyster does not attain its majority until the third or fourth year, and produces the greatest quantity of spat from the fourth to the seventh year. The spatting season usually commences in May, but depends much on the temperature, being deferred till a later period in a cold season. In a warm lake on the south coast of Sweden-which forms a natural hothouse for oyster-cultureoysters are found to contain ripe spat as early as the end of March. The spatting season may continue until the end of September. And one of the most curious facts in the natural history of the oyster is this: that so soon as she has laid her eggs the mother-oyster changes her sex and becomes a male. Whether this change of sex takes place several times in a season, and if so, how often, is not known. It is a curious arrangement: but, depend upon it, it has not been instituted by Nature without a purpose.-PROF. C. LLOYD MORGAN, in Murray's Magazine.

WEATHER CHANGES.

No subject is so much talked about and so little understood as the weather. Men are still to be found of excellent education in other respects who connect change of weather with the phases of the moon, and consult their almanacs for rain or fine weather with all the credulousness of Zadkiel. These empirics swear, it may be, by the Shepherd of Banbury, and eagerly watch, like him, in what direction a sheep looks when it first rises, or whether a swallow flies low or high. Others observe the barometer, and perhaps register its figures; but are so little acquainted with the conditions of weather that when the glass rises during rain (owing to the observer being in front of a cyclone) they are inclined to doubt the sanity of their oracle, and to follow the old gentleman's example who, under such circumstances, opened the window and flung his barometer out on the lawn, exclaiming, "Perhaps you will now believe that it does rain!" Yet a third group of the unscientific weather-wise revel in statistics of rainfall, forgetting that these can only show the climate, not prognosticate the weather of any locality, which is due to the distribution of surrounding pressure. To obtain a knowledge of this it is necessary to search the daily charts issued by the Meteorological Office; and to peruse them to advantage the student must be well acquainted with the exact meanings of isobars, anticyclones and hemicyclones, cols, depressions, and gradients. This is one branch of his subject on which Mr. Abercrombie in his Popular Exposition of the Nature of Weather Changes from Day to Day, be

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stows much care. Then he explains the character and value of variations-how diurnal variation modifies but never alters the eral character of the weather. Thus his readers are conducted to the methods of forecasting which are at present in Vogue.

First, are pointed out what helps a "plain man, as Macaulay called an ordinary man of common-sense, has besides his senses to warn him of storms ahead; next the extended wisdom of the public meteorologist is estimated, of him who in his office receives periodical barograms from the Atlantic, puts together synoptic charts, and adds his own knowledge of the nature of the weather and the motion of depressions in his district. Thus, feeling the pulse, as it were, of the approaching weather, the modern scientific meteorologist issues his forecasts, and, it may be, saves much valuable property and many still more valuable lives, appearing to rival Jupiter or Eolus in his power over the winds and waves. An exhaustive treatise on modern meteorology has long been desired, and Mr. Abercrombie has herein done his best to supply it. It will not only satisfy the needs of the student; but, as enabling them to appreciate the information supplied to the papers each morning by the Meteorological Department, seafaring men, farmers, and country gentlemen will find their account in reading this book.

After some paragraphs on the use of synoptic charts, the author explains with useful diagrams the seven fundamental shapes of isobars-lines of equal atmospheric pressure on the due consideration of which, in juxtaposition with the diurnal influences of the observer's locality, all true prognostication of weather is founded, according to modern meteorologists. An excellent chapter on clouds succeeds, paying especial attention to the cirrus. Following Ley, Mr. Abercrombie attaches especial importance to this form of cloud when considered in reference to its surroundings; indeed, "the most valuable addition of recent times to weather-lore is undoubtedly in the methodical observation of cirrus clouds." In short, with one eye on the clouds and the other on his barometer, even if unaided by telegraphic messages, an observer can, after a somewhat empiric fashion, forecast his own weather fairly well. The author generally points out the grain of scientific truth which frequently underlies popular weather proverbs; and it is amusing to hear with what gravity he draws deductions from the fact of the scalps taken by the New Mexican Indians growing damp before rain. "From this," he says, "we may assume that scalps are slightly hygroscopic, probably from the salt which they contain." It is matter of the commonest observation that all hair becomes damp before rain.

The more advanced chapters of the book give instances of cyclones with their interpretation from barograms, and explain the importance from a national point of view of careful and successive meteo

grams for any useful weather prognostication. The influences of heat and cold, of wind and storms, upon the climate of any place as well as upon the weather to be expected, are elucidated, and by the aid of figures, synoptical charts, and meteograms, made clear to the most ordinary understanding. There are two good chapters on the local and diurnal variation of weather, after perusing which, the reader should be able, not only to estimate the factors which make up the weather in his own locality, but also the data required for national forecasting. This is mainly a question of money to procure a succession of barometrical readings, and of skilled observers who can read these barograms with a careful eye to local and diurnal variation around them. Meteorology is certainly not at present (although its students hope it is always drawing nearer to it) an exact science. The best prognostics are liable to disturbing influences, which have not been taken into account. Only a percentage of forecasts can reasonably be expected to turn out correct. A much larger percentage, however, when thus scientifically calculated, is claimed as correct by modern meteorologists than would be the case were the weather merely estimated empirically, and, as it were, by rule of thumb. "Natural aptitude, and the experience of many years' study, are" still "the qualifications of a successful forecaster.

How completely weather can upset calculations was curiously shown when we were reading this book. Throughout autumn the prevailing tone of British weather had been persistently anticyclonic. On the evening of October 21 the conditions were threatening, and the cone was hoisted for a southerly gale in some of the districts. On the next day (Saturday), however, the barometer rose, and some improvement in the weather was manifest. But that evening a cyclone was brewing at the mouth of the Channel and traveling eastward at a great rate; the barometer fell rapidly, and a gale speedily swept over the Channel Islands and the southern coast of England, fraught with some loss of life and much damage to shipping. It has been pointed out that for rapidity of formation and motion very few parallels to this gale exist. It has been compared to those of October 23, 1883, and of November 1, 1872. The Swiftness of the career of these gales was so great that they did not allow time for mariners to get out of their way. Unless the officials at the Meteorological Office had been at their posts all night, and been furnished with frequent telegrams of the weather in the southwest, it would have been impossible to forecast these gales. In short, if government is to do its duty by our seafaring population, in order to insure reasonable correctness in the weather forecasts, more money must be expended. Whether it is worth while doing so may be judged from the consideration that not property so much as lives are at stake.-M. G. WATKINS, in The Academy.

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