whose wants Divine Providence has not overlooked. Their affinities in nature are with the diatoms and certain species of algae.

We only intend speaking of the commoner forms, which, fortunately for our friends, are inferior to none in beauty, and afford to all microscopists, young and old, the greatest pleasure, and ample scope for the use of the highest and most perfect powers in their examination.

this, but our examinations have not been careful to the degree which the observers referred to insist upon. Pritchard seems to think there is a possibility of an optical delusion.* While looking at these organisms, they will be observed to move slightly, but the means by which this is effected have, as yet, eluded detection.

The other evening I saw the end of a bright-green Closterium seized by a large animalcule, Notommata myrmeleo (?) and subjected to the action of the teeth. Soon, I found that the particles of chlorophyll were leaving the desmid, and passing down the gullet of the animalcule, evidently by suction, and I watched them with great interest; firstly, because I never before saw a rotifer taking a salad in so civilized a manner (for they generally transfer their vegetable diet into their crops by a rapid jerk, particularly when it is small enough to go down whole); and, secondly, because apertures at the ends of the frond are not generally believed in. When the animalcule had finished its supper, that is to say, when every particle of nutriment was extracted, it cast the empty frond among others that were strewed about, and I could not detect the slightest rupture in the delicate transparent case which a few moments before was so full of green contents. There may have been one nevertheless.

One of the most common bears the name of Closterium. The various species, of which Pritchard mentions some thirty-six, or thereabouts, are more or less crescent-shaped-some being nearly straight, and others curved like the new moon. The surface in general is smooth, but there are many examples of its being delicately striated. At each end of the frond there is a "terminal clear space, in which are active granules." These require a 4-glass to show their extraordinary dancing movements, as if each had an independent, merry existence.

With bright illumination (and obj.) one may see, just beneath the surface, that the particles of endochrome are seldom stationary, but in general move steadily up or down the frond, and no difficulty will be experienced in following with the eye the course of the circulation at the edges, where some have asserted they have seen cilia. We have never seen

Fig, 96. End of frond of Closterium lunula (showing active granules in chamber at the end; the arrows indicate the directions of the surface circulation) x 500.

The mode of reproduction in Closteria is twofold (?), by self-division and by conjugation. In every frond of Closterium will be noticed a central clear space, dividing it into two segments. Here a gradual separation takes place, occupying some hours before it is completed. The separated halves then each commence to grow independently, till ultimately a copy of the parent form is assumed. This is an outline of self-division. Conjugation is a different process; two individuals approach each other and come into contact. They then intermingle their green contents and a curious globular + body

* Other authors deny the existence of cilia in the desmids altogether.

† Not globular in all desmids.

is formed, called a sporangium, which is believed in due time to produce a multitude of individual spores, ultimately growing to Closteria. The operation of forming a sporangium is said to be very rapid, only occupying a few minutes. We have never been fortunate enough to witness it. A third mode of reproduction (in Cosmarium) is suspected, and mentioned in Pritchard. To this book, embodying the observations of a host of inquirers, we refer the reader for the fullest information, up to the present time, attainable. At most, however, very little is known of the desmids, and if the readers of SCIENCE GOSSIP will set to work, providing themselves with the home-made growingslides invented by Professor Smith, of Kenyon College, U.S., or with Mr. Beck's improvement, the results attained will repay them; provided they diligently search after truth, rather than advance speculations. The "Micrographic Dictionary" says, "No less than four modes (of reproduction in desmids) have been observed, and many points connected with the subject still remain to be cleared up."

While we write we have under examination several species of Closterium, which were gathered at Keston, on the 18th December last, and have been kept in a bottle ever since (two months), without detriment.* We think the reader will readily identify the forms figured. One of the largest and most beautiful is C. lunula, the end only of which we have drawn, because, on the same scale, it would have filled our page entirely.

Fig. 97. Euastrum oblongum (front view) x 250.

Another kind of desmid introduces itself under the name of Euastrum. This is somewhat lozengeshaped (in front view), with rounded protuberances or inflations, and thicker near the middle than at the edges. The central division is strongly marked. We figure examples of E. oblongum in different positions, that some notion of the shape may be obtained. The endochrome is of a beautiful herbaceous green, but then this colour is common to all desmids, so we need hardly notice it. Occasionally circulation may be seen in the interior, but not often. There are many species of Euastrum,

* Except such as have been eaten by various animalcules and crustacea; by no means an inconsiderable number.

*

spines. We have never observed circulation so as to be certain about it, but have often seen the swarming motion of the particles of eudochrome, believed by many to be connected with some mode of reproduction only partially described, and not understood. Since last December up to the present time (Feb. 21) we have hardly examined one Cosmarium without noticing this peculiarity. At page 201 in SCIENCE GOSSIP, Vol. I., will be found a very good account of the mode of reproduction in Cosmarium Botrytis both by cell division and by conjugation.

Some desmids are very minute-Ankistrodesmus, for example, which is described as like a tiny bundle of faggots. Others appear as jointed chains enclosed in a glassy tube. Many, also, are so curious that no description without a figure would be intelligible; but we cannot at the present time enter more minutely into their characteristics.

The name Desmidiaceæ is derived from a word signifying a chain, and is descriptive of the appearance of many members of the family.

A pleasant writer in "Recreative Science" suggests that our jewellers might copy these microsopical plants with advantage to themselves. The idea appear to us to be a remarkably good one, and could they only imitate, in suitable materials, the display of beauteous forms, and delicate colours, so suitable for brooches, clasps, chains, bracelets, &c., which offer themselves in the Desmidiaceæ, the public would not be slow to appreciate their efforts.

Before we conclude we will say one word as to the collecting. When in large quantities, they give a green tinge to the surface mud where they lie, and in this case the bottle must be filled with water as nearly as possible at the bottom. Invert it, and when it reaches them turn it on one side, and the contained air will escape while the light mud, with

however, is to strain the water containing them through linen, and, when sufficient quantities are obtained, to remove them from the linen to the stock-bottle.

We must not dismiss the subject without alluding to the power of motion which the Desmidiaceæ possess. Under the microscope several species may be seen to move slightly, and they are believed to retire in dry weather below the surface of the mud, where they dwell while it is soft, and when it is overflowed with water again, to reappear in the light of day, which they seem to love. If kept in a window, the greater part will make their way to the side of the bottle next the light, and numbers will attach themselves in some mysterious way to the glass, at various distances, from whence they cannot be dislodged without a smart jolt. Their small specific gravity, and the mucus in which they are enveloped, perhaps render them important aid in effecting this object.

Having seen, at a recent meeting of the Microscopical Society, Messrs. Powell and Lealand's marvellous exhibition of the circulation in Vallismeria spiralis under their new binocular and 1-16th object glass, we were tempted to ask them to permit us to see more of the arrangement. With the courtesy which these gentlemen always display, they invited us to their manufactory, and to our astonishmemt showed the Amician test (Navicula rhomboides) stereoscopically, the markings being resolved into checks in such a manner as we never saw before.

We then took from our pocket a small bottle containing some of the desmids we are describing, and with the help of Mr. Powell commenced an examination of them under conditions which a month or two ago would have been considered incredible, viz., an amplification of 600 diameters and upwards, and the binocular relief as satisfactory as the most fastidious examiner could wish.

S. J. M'INTIRE.

ANIMALS IN AQUARIA.

to squeeze handfuls of the moss containing them into a large bottle. When the bottle is full of water the light sediment will be found rich in them. Sometimes the hand alone will have to be brought into requisition, to convey such as are known to be attached to the stems and leaves of aquatic plants to the surface. The most elaborate plan of all,

* We may be under a misapprehension in this, and the specimen of an empty frond we have drawn, may be either a variety, or a totally different species.

ed. 1856, p. 224, tells his readers that if they procure a few bits of weed-covered rock from the level of low water," and place them in a glass vessel of sea-water, many very interesting creatures will creep out of the interstices of the stones and plants growing on them. I have been in the habit of thus procuring and observing small animals for some years, but I do not find anything so productive of such things as Serpulæ masses, and the various substances upon which Serpule grow, when dredged from the Bay of Weymouth, in Dorsetshire. No

other locality known to me is so rich as this in the particular objects under notice. The substances to which the Serpule adhere are stones; old shells, both bivalves and univalves; broken or whole wine or beer bottles,-these bottles, especially, are very full of various things, both inside and out, and broken crockery. Not merely Serpula of two or three species are on these masses, but several species of Sabellæ, and other tubiculous worms, such as Spio, Terebelle, and others; and adhering to them, in considerable abundance, are small sea-cucumbers (Ocnus), and within the empty univalve shells, such as those of Buccinum, are frequently found specimens of a somewhat rare vermiform echinoderm, Syrinx Harveii. But the great value of these dredged masses does not consist merely in what is found upon them when first got, but also in the highly-interesting things which will grow upon them, from germs not at first seen, when they are properly treated in an aquarium. Here I have one large tank, of 300 gallons capacity, with a stream of sea-water running through it day and night, at the rate of 100 to 500 gallons per 24 hours, according to circumstances, and which is stocked mainly with Weymouth Serpula, and other creatures naturally associated with them, or grown here on the same masses: I even grow Alcyonium on them. The animals, however, which spring up with greatest vigour in confinement, attached to the same stones, shells, and broken glass and crockery, are Tunicated Mollusks, of various sizes. These are without any shell, but are covered with a leathery tunic,-hence their name. Some of those I grow are of the simple or solitary kinds, i. e. which are not organically connected in masses, like the compound species, and look, as they stand up, permanently fixed to foreign bodies by their base, like miniature semi-transparent double-necked bottles. (See Hardwicke's SCIENCE GOSSIP for February, 1866, pp. 30-32.) These are Ascidians, and in the Serpula tank No. 6 of this establishment, and in all other tanks where Serpule are contained, they swarm by hundreds, nearly all of them having made their appearance in situ ; and these specimens are much cleaner, and are therefore better for examination, than those obtained grown in the ocean. The simple kinds I mostly grow are, Ascidia virginea, A. mentula, Molgula tubulosa, Cynthia quadrangularis, C. grossularia, and others; and the compound kinds which spring up are of two species, namely, Botryllus polycyclus and Clavelina lepadiformis. The Botryllus comes in patches, in twenty or more places at once; and it looks like groups of brilliantlycoloured violet stars set in firm jelly of a darker hue, and after a time it goes away. I have reason to suppose that excess of light is one great cause of their disappearance, for the only colony I now (February 1st, 1866) possess (and which I have preserved all last summer, after all the rest went away

in the spring) covers a surface of Portland cement in a corner of a tank which has been purposely, for another purpose,* closely covered by a board. I have often obtained Botryllus from the sea, but have never been able to keep it long; and I remember that, about twelve years ago, after many attempts were made to acclimatise it in the Regent's Park aquarium, London, a great patch, larger than one's hand, and containing several hundreds of individuals, made its appearance, unbidden, on the slate end of one of the tanks.

Clavelina comes similarly in great colonies, chiefly in spring and early summer, standing up like groups of little clear vases, much less opaque than when I obtain them from the sea ready grown, and less liable to die. But, whether grown or introduced as adults, they disappear after a time, being killed off, as I believe, by the great enemy of most of these beings, light. Clavelina is small enough to be placed in a zoophyte trough on the stage of the compound microscope, and the circulation of its fluids produces a beautiful spectacle, which is figured in one of the plates to Mr. Gosse's book, "Tenby; a Seaside Holiday." 1856. I should mention that the two compound Ascidians named do not commonly grow upon the Serpula masses, like the simple kinds, but rather through their influence; not only because of the germs introduced with or upon them, but because, as well, of the healthy influences of the numerous forms of alge also growing upon them; and their roughness of surface, or some other conditions, seems peculiarly adapted for encouraging the growth of other kinds of seaweeds, so that our Serpula tank is eminently a very healthy one, not easily put out of order, and with its water ever brilliantly clear. Sponges, too, like the Ascidians, are things which are not easily kept when introduced in aquaria when ready grown; but they may be maintained for long periods when they grow up by chance; and upon the Serpula masses here, or in the Serpula tank, I have now growing (and bred here) five or six species in a state of great vigour, as, e.g., Sycon ciliatum, Cliona celata, Grantia botryoides, Halichondria panicea, Leuconia nivea, and two others which I cannot name from any books in my possession. Some one, in Hardwicke's SCIENCEGOSSIP, a little time ago, asked how to keep the Freshwater Sponge (Spongilla fluviatilis). I do not know, as I have often tried, and always failed; but here, at any rate, is evidence that the dredged masses I am writing of, will, if placed under favourable conditions, produce many things, and, among others, marine Sponges. At the Birmingham meeting of the British Association, last summer, I saw reported in the Athenæum, that Mr. W. R. Hughes

*February 25th. I have just discovered another small colony, on the under part of the shell, of a large living spidercrab-Maia Squinado.

had succeeded in keeping a living marine sponge, but the species and the circumstances were not mentioned.

I should name that it is not always safe to place these dredged masses, when got fresh from the sea, into ordinary aquaria without preparation, as there are almost sure to be upon them some animals more delicate than others; and if these are below the mass, between it and the floor of the aquarium, they probably will die, and their death spreads destruction to other things around; and so, a small streamless tank, with an amount of aeration barely sufficient for its ordinary wants, is thus apt to become quickly and injuriously affected throughout. Accordingly, when in trade in London, I used, as a means of safety, to be obliged, with much regret, to carefully scrape and wash away all matters, however interesting, from these masses except the Serpula themselves; and in no other state could I sell them to my customers without chance of disaster.

Here, however, I am only too glad to get such masses just as they are dredged, no matter how large, or how rough, dirty-looking, and scabrous; and I place them first, and for some time, in great shallow probationary troughs, with a strong stream of sea-water running through them day and night, and I turn over the masses occasionally, so as to present all their sides equally to the oxygenating influences of the current, and to check the tendency to decomposition which exists when the underlying parts of the masses are in close contact with the sand and shingle forming the bed of the troughs. When this is done, and all is healthy, and there seems nothing else likely to die, the masses are transferred to the show-tanks, and when anything grows up upon them in the manner described, I am very particular in keeping it in exactly the same spot as that in which it made its appearance, as often a removal of but a few inches disturbs some delicately-balanced conditions, and a sudden disappearance is the result.

The mention of sand and shingle in aquaria reminds me that some early writers on the subjectthe Rev. Messrs. Kingsley and Tugwell, for example-advise that no sand or shingle should be in aquaria, as they encourage the formation of the blackness which is a sign of the presence of sulphuretted and carburetted hydrogen gas, resulting from the decay of organic substances. Fine sand is even worse than coarse, as the particles lie so closely together, and around any object resting upon or in it, that water cannot freely circulate around. But the discomfort to the animals, and the unsightliness of a bare slate or glass bottom in a tank, by far outweigh any advantages to be derived from the absence of sand and shingle; and, indeed, no blackness will form unless some decomposing substance is carelessly suffered to remain in the aquarium; and when that is the case, its removal, and the

gentle stirring up of the sand at the spot affected, will cure the evil in a short time. And as to the black layer which will always in time accumulate at the bottom of the layer of the gravel, below its surface, and which cannot be prevented by any amount of good management, and which it is probably not desirable to prevent, as many animals seem not to dislike it by the manner in which they burrow in it, -that is harmless, so long as it does not crop through the surface.

I have to remark, that Mr. Shirley Hibberd, in last November's number of Recreative Science, advises aquaria to be built up internally with old oyster-shells which have for a long time previously been exposed to wind, rain, and drought, to destroy any germs of animal life happening to be upon them, and which, by decaying, would prove hurtful to other things. But this killing of all germs would deprive the shells of the only value they can possess, as they then would have no more worth than any other rough substances for the growth of algae upon them; and it is contrary to good taste to introduce dead shells in an aquarium merely because they are shells, or because they are rough. Rough stones would be much better, and more naturallooking. W. ALFORD LLOYD, Zoological Gardens, Hamburg.

PIN CENTRES AND ROSE CENTRES.

IF any one will take the trouble to examine a bank

of primroses, it will be seen that the flowers are by no means all alike. There is a great variety of colour: here and there one almost pure white; a few almost lemon-yellow, with every possible shade between. They differ, too, in their form: some having a starry appearance, because the segments of the flower are narrow; others looking solid and round, on account of the segments being broad and lapping well over each other, and these last are by far the handsomest flowers; so that, if one wished to transplant primrose roots into a garden, the trouble of selecting plants would be well repaid in the effect produced.

But there is, physiologically, a much more important difference in primrose flowers than either the colour or the form. On some roots the flowers have the pistil much longer than the stamens; on other roots the stamens are much longer than the pistil. In the first case there will be seen the pistil, resembling a pin's head just within, or even protruding from the throat of the flower, no stamens being visible, because they are situated low down in the tube of the corolla. In the second case, the stamens are seen forming a pretty coronet, which closes up the throat of the flower, entirely hiding the pistil, which, indeed, does not reach more than half way up the tube of the corolla.