this means twenty-six pages would be employed instead of one, yet the subdivisions would be so much smaller than by the usual method that the extra labour would be fully compensated for. Thus the heading for the first page would be aa, ab, ac, ad, &c., and for the second ba, bb, bc, bd, &c. Notwithstanding some columns, such as bb, would, most probably, not contain a single entry, yet I should retain them, for the eye soon becomes accustomed to the position of the column for each letter, and knows at a glance the spot where the entry should be made.

If you think this plan will help Mr. Mott and others, I hope you will find room for it; if not, please consign it to the waste-paper basket. ALEX. E. MURRAY.

No doubt many of those who have found the teeth and scales of extinct ganoids have been puzzled by not finding their entire skeletons. This is owing to these fish not having possessed entire bony skeletons: consequently,' the cartilaginous portions of the fish have perished, whilst the teeth and scales have been preserved. In Megalichthys, however, Professor Huxley has discovered a ring or hoop of bone in its vertebra, whilst the rest of its skeleton consisted of cartilage.

AT

CARBONIFEROUS FISH.

T the base of the coal-measures there occurs in Yorkshire a bed of coal which is different from any of those above it. This bed-the Halifax bed-is covered by a "roof" unlike that of any other coal-bed above the mountain limestone, and consisting of nodular concretions called "baumpots," which contain not only the remains of plants and fresh-water shells, but also of fish and marine shells. The floor or sill of the coal of this series, instead of being, as in the other series, a peculiar fine clay, full of stigmaria, consists of ganister or galliard, a hard siliceous sandstone full of the roots of plants. The presence of this stone consequently furnishes an exact indication of the position occupied in the coal-measures of that stratum in which it is found.

In the "baum-pots" before mentioned I discovered last July, when staying in the neighbourhood of Leeds, several remains of fish, both scales and teeth, belonging to Agassiz's two great orders of fish, the Ganoids and Placoids.

The ganoid fish have been thus named by him on account of their being covered by enamel so hard that, if struck with steel, they will emit sparks like flint; thus differing from the fish belonging to other orders. Another peculiarity attaching to them is this,-the union of reptilian with fishlike characters, they being able to move the head upon the neck independently of the body, and the connection of the vertebræ by ball-and-socket joint, instead of by inverted cone, as in the ordinary

fishes.

The representatives of this order of fishes are the Lepidosteous, or bony pike, and the Amia of North America, the Polypterus of the Nile and rivers of Senegal, and the Ceratodus of Australia. As all these genera inhabit fresh water, analogy points to the conclusion that their carboniferous ancestors lived in the same element.

Fig. 110. Ganoid Scale of Megalichthys.

Of the scales of these fish examples are given That of Megalichthys Hibberti (fig. 110) is of a smooth rhomboidal form, with minute punctures that are connected with one another by means of canals.

The other scale, that of Acrolepis (figs. 111 and 112), is similar to the foregoing in shape, but differs from it in having its surface marked by deep channels. The former genus is found only in the carboniferous system, whilst the latter is found both in the carboniferous limestone of Derbyshire, the millstone grit and coal-measures of Yorkshire and in the Permian of Durham.

Figs. 111 and 112. Scales of Acrolepis.

The other great order of fishes, the Placoids, represented in our time by the Sharks, Dogfish, and Rays, have been so named by Professor Agassiz because they have their skins covered irregularly with plates of enamel, often of considerable dimensions, but sometimes reduced to mere points, like the shagreen on the skin of the Shark or the prickly tubercles of the Ray. The fishes of this order had cartilaginous skeletons, which were soon destroyed after they had perished.

The teeth of these fish are of two kinds,-either sharp and pointed, or massive palatal teeth, fitted for grinding. Of both these we have living examples; those of the Shark being representative of the former, and those of the Cestracion, the Port Jackson shark, of the latter.

Fig. 113. Tooth of Cladodus. Fig. 114. Tooth of Orodus

Of the former we have an example in the tooth of Cladodus (fig. 113): this is a sharp conical tooth covered with shallow striations; whilst of the latter the teeth of Orodus (fig. 114) and Psammodus are instances. The former presents a serrated edge, whilst the latter is perfectly smooth.

Such are the characters of some of the fishes which formerly roamed in the carboniferous seas. Though but little is at present known of them, that little is sufficient to fill us with admiration of the wisdom and power of Him who has created all things. REV. W. H. PAINTER.

HOW TO CUT VEGETABLE SECTIONS.

BY WALTER WHITE.

“WE E want pretty and interesting objects."

This is the cry, which waxes louder in proportion as our ranks are augmented by the enlistment of fresh recruits. Let me commend to their notice sections of stems, leaves, seeds, and other portions of plants. They are pretty, as well as interesting; easy to mount, and moreover, when well mounted, very permanent. How to cut them is the rub. This seems to be a great stumblingblock; consequently we find very few amateurs' cabinets containing a really good selection of vegetable sections. One will tell you he hasn't time to cut them; another, that he has tried and failed;

X

proverbial conquerors, of all difficulties, namely, patience and perseverance. Assuming the reader to possess the two latter, I will proceed to put him in the way to possess the former.

I first began to think of cutting sections on September 1st, 1866, from seeing on that day, in SCIENCE-GOSSIP, a description of an instrument which I, in my innocence, then thought would answer that purpose. How anxiously I tried shop after shop before I could find the one where I could invest my penny in a music-binder! I need scarcely say the affair was a failure. Some time afterwards I got a watchmaker to cut me a screw, with which, a fishing-rod ferule, and a bit of brass plate, 1 knocked up an uncouth-looking picce of apparatus, which served my purpose pretty well for a long time. Yet, as the screw was not so fine or so well fitted as I could have liked, I cast about for a friend to cut and fit me a better. After many inquiries, I came into contact with a gentleman who very kindly recommended me to try wedges instead of the long-sought micrometer-screw. I took my nondescript to pieces, and in a very short time converted it into a machine, which, for truthfulness, simplicity of manners, and withal lightness of figure (in the cost thereof), leaves little or nothing to be desired. Here is an outline sketch of the apparatus, fig. 115; here also is the receipt for making it. Take a brass tube (fishing-rod ferule), T, about of an inch diam., and 14 in. long; inside of this

while a third has heard so much of the difficulty of section-cutting from those who have attempted it, that he thought it useless to go to the expense of a machine. Now, I hold that everybody who takes up the study of Microscopy ought early to learn how to make a good microscopic section. In Histology this acquisition is indispensable. As a means of mastering the art, nothing can be better practice than operating on the subjects beforementioned. There is no royal road to sectioncutting, any more than there is to other branches of Microscopy; yet a few practical hints may smooth the path a little, and tempt a few to turn some of their leisure moments in that direction.

The first thing necessary is a section-machine; the second, a sharp-cutting instrument. Besides these, two other things are also needed-those two

tube fit a brass plug (P) of the same length. When smeared with tallow, this should fit the tube with a water-tight joint. Solder one end of the tube (T) into a hole that will just receive it, in the centre of a brass plate (X) 3 in. × 1 in., and about -in. in thickness, having a hole at each corner to pin or screw it down to the block (B). This is the metallic portion, which any country tinker can easily make. The wooden portion can just as easily be made by any country carpenter W, W, two wedges, each 15 in. long, in. thick, and 1 in. deep at the base of angle. They should be worked up true out of a thoroughly sound piece of beech or

a

Fig. 116. Section of ditto.

mahogany. Cut two other wedges of the same angle, but rather longer, in. thick, and attach one to each side of the wedge, which is to be stationary, so as to form a groove to steady the loose wedge. This grooved wedge fix to a deal board (D), 15 × 34 by screws (S). Now comes the block (B) of beech or mahogany, 23 × 3 × 13. Through the centre of its longest axis drill a hole to receive the tube (T). Below the tube, and through its shortest axis, sufficient of the block is to be cut away as will span the fixed wedge. The block is firmly fixed by long and stout screws to the board D, in the position shown in the figure. The tube T is now inserted in the hole, and the brass plate (which I omitted to say should be perfectly flat and smooth) is screwed or pinned down to the block. On the face of the lower wedge gum a piece of paper, with lines ruled on it about 3 of an inch apart, and the machine is complete.

The best cutting instrument, in my humble opinion, is a razor. A small one, made of "good stuff," should be selected. If the blade is fixed in a small bradawl handle, it will be more convenient to use. As it is perfectly useless attempting to excel in section-cutting with a tool that will not stand the usual test of cutting a hair, the reader, if he be not endowed with the accomplishment of razor-sharpening, had better make friends with some one who really is, and take a practical lesson or two.

Supposing the reader wish to try his 'prentice hand upon a wood stem (transversely), this is the way to proceed :-Get a cork and trim up so as to fit the tube rather tightly; with a cork-cutter make a hole through it in the position shown at a, in fig. 116, which should be the least trifle less in diameter than that of the stem. Next divide the cork lengthwise at b, taking care to escape the hole. Cut out the shaded portion (C), which is to be replaced by an exact counterpart of deal. Cut off an inch of the stem and place in the hole (a); put the pieces of cork and deal in their places, and push all gradually down the tube, with C towards the operator, the plug (p) resting on the thin end of the loose wedge. Have at hand a glass vessel of methylated spirit, and all is ready for work. Tap the wedge with the back of the razor till the stem just appears above the plate; then dip the razor in the spirit and take off a slice, cutting no further into the deal than is necessary. Cut off a few more slices, till you begin to feel used to it; then strop the razor afresh and see how thin and perfect a section is to be obtained, making use of the ruled lines as a guide for the distance the wedge has to be forced. An herbaceous stem will not require the cork and deal packing. Strips of the same stem will answer better, care being taken to pack firmly without crushing. Leaves will generally be placed between the two halves of a cork cut lengthwise;

while seeds and other small things, such as unripe moss capsules, are best held in a mixture of wax and spermaceti. This is the modus operandi: Pour into the tube, in a molten state, a mixture of about equal parts bees-wax and spermaceti, and just before it solidifies place the seed in the mixture, in the desired position. When quite cold, the wax will fit the tube loosely: a thin splinter of deal forced down the tube will make it firm. This is also one of the best plans for vertical sections of stems.

Some recommend cutting towards, and others away from, the operator. I prefer the former method. Keep the razor well wetted; hold it firm and cut steadily, using plenty of the edge. The sections will generally stick to the razor, and can be shaken off into the spirit as fast as they are cut, thus keeping the razor constantly wet with the least amount of trouble. No rule can be given as to the thickness the sections ought to be cut; it depends upon the size of the cells to be brought into view. The smaller the cells the thinner the section, and vice versa. A good transverse section should show the pith, wood, and bark all the way through, without a flaw. Wood stems should be gathered in the autumn, and placed immediately into spirit. They are never scarcely so good if allowed to dry. A good plan for identifying the stems after they have been soaked, is to cut on one end a Roman numeral, against which in a book the name is placed. Without some precaution of the sort, it may be rather embarrassing to a beginner to know which is which, out of a bottleful of stems that have lain by for some time.

Herbaceous stems should be cut as fresh as possible, and the sections allowed to remain in spirit a day or two, to empty the cells of chlorophyl, after which they should be well washed in clean water. Seeds are in the best condition for cutting just as they are ripening.

I have but little to say about the mounting. For transparent slides, perhaps there is no better plan of mounting the wood and seed sections than in balsam or damar. Some of the transverse wood sections, for example, Clematis and young stem of Dog-rose, when mounted dry and revived by reflected light, are exceedingly beautiful, especially if a bright blue ground be used. Sections of herbaceous stems and the softer tissues of vegetables show best in fluid. To some of the thousands of ardent lovers of Nature, subscribers to SCIENCEGOSSIP, I would fain believe my simple sectionmachine will be welcome. Every botanist now has a microscope; yet how few, amongst their collection of slides, can show a dozen good sections of their own preparing, illustrative of the physiology of the plants they take such pains to collect, dry, and classify. In their case, a little practice at sectioncutting would throw open new sources of pleasure,

increasing the interest already attached to the beautiful study of botany, and adding yet deeper feelings of reverence towards the great Creator.

THE CRAB A GEOLOGIST.

THE following notice of a natural phenomenon which I witnessed may be of interest to readers of SCIENCE-GOSSIP :

As I was walking with a friend, some ten years ago, along the sandy shore of the Tenasserim coast, I was surprised to see in one place a large number of apparently rolled pebbles or stones extending along the beach for some distance, just above highwater mark. The reason for my surprise was that such a thing as a pebbly beach is nowhere met with (at far as my experience goes) on this coast. The entire coast-line of Tenasserim, from Amherst on the north to the Packchan river on the south, consists of alternating bold granite bluffs, which jut out into the sea, and semicircular sandy bays, with here and there an extensive mud-flat and mangrove swamp at the mouths of creeks and rivers. It is very hard to find a stone anywhere on any of the sandy beaches. Granite boulders of various sizes are frequently met with on the sand, but that is all. The very unusual appearance, therefore, of a number of stones, resembling shingle, collected together in one place, surprised me.

After my companion and I had amused ourselves with throwing about some of these stones, which were so hard as to have required a hammer to break them, we found that others (those nearest to the sea) were soft-of a firm cheesy consistency-so that the end of a walking-stick could be forced into or through them. This naturally increased our surprise; we therefore set ourselves to discover, if possible, the cause of this strange phenomenon. We were not long in doing this. The actual process of manufacture was witnessed. It may be stated here that the part of the coast spoken of is not far from the mouth of the Tavoy river, which expands into a broad estuary several miles across. This river carries down towards the sea a vast quantity of mud, the greater part of which is distributed along the coast-bottom to the south, owing to the direction of the river, which flows from north to south, the run of the coast-line being the same. At Mergui, also, only sixty miles to the south, another arge river, the Tenasserim, pours down its quota of mud, and this also is confined near the coast by the islands of the Mergui Archipelago, which stretch from near the mouth of the Tavoy river on the north, to near Junk-Selung on the south. I have dredged the bottom at intervals between Tavoy and Mergui, and found it to be mud the whole way inside the islands.

The consequence of this is, that although some of

the reaches of sand on this part of the coast are very fine, the sand is, nevertheless, comparatively shallow, and it fines off rapidly to seaward, until, a little way out, pure mud is reached. In some parts, at low water, a very thin layer of sand covers the mud below. This mud is exceedingly stiff, and of the colour of the well-known blue lias. To come now to the manufacture of these stones. The crabs, which abound on tropical seashores, were here, although too small to be worth catching for the pot, considerably larger than I had seen in similar situations elsewhere; and, as the tide was low, we saw numbers of them running about the wet sands, and, as we approached them, they would dive rapidly down into the small round holes which it is their habit to burrow for themselves. In making these holes the crabs (as is, no doubt, known to many) throw out the soil in small round pellets or balls. I had frequently noticed at Amherst the tiny round balls of sand strewed about the holes which the smaller crabs there make. When the ejected material is sand, these balls are, of course, at once dissolved at return of each tide. But here, as the sand was only in a superficial layer, and the crabs were larger, in making their holes they penetrated through the sand and reached the mud; consequently the material thrown up was stiff clay, and the balls were larger in proportion to the size of the workers. Looking at these balls of clay as the tide was turning to flood, we soon perceived how our stones were made. The ripple of an advancing wave would first roll two of the smaller balls into one, then another wave would do the same with two larger ones, until, by a repetition of this very simple process, rounded balls of various sizes were formed, and ultimately, as the tide advanced, flung up high and dry upon the sand, out of the farther reach of the waves. Here they lay and hardened, until, in form, in weight, and in general appearance, they resembled bona-fide water-worn fragments of blue lias. There was a long line of these stones on the sand just above high-water mark, and they must have been numbered by thousands.

And, now, to offer a remark or two on this subject. It is easy to imagine that these stones, so strangely originated, may, at some distant day, be imbedded in a stratum of sandstone, and may, peradventure, form the subject of investigation by some future geologist (supposing, that is, the race o geologists to bejas enduring as the strata which they make their study), and if so, they would probably be pronounced to be genuine waterworn fragments of rock older than the sandstone in which they were found imbedded. In this instance, our imaginary geologist will have been mistaken; for though indeed formed partly by the action of water on a seashore, they were so formed by a constructive, and not a destructive, process; and, moreover, they would be of exactly the same age as the sandstone.

But, if stones are being occasionally formed now by the singular method above described, why may they not have also sometimes been formed in a similar manner in the remote ages of the Past? It crabs, as is likely, inhabited primeval seashores and disported themselves upon them as they do now (I am, unfortunately, not geologist enough to know it there be any evidence to this point), then the same agency may have been at work in the formation of similar stones now found imbedded in existing strata, and pronounced to be waterworn pebbles of an older rock; and then also, some stones, so pronounced upon, may possibly have had a different origin from that which has been assigned to them. In ninety-nine cases out of a hundred probably, the commonly assigned cause would be the true one; but the little fact which I have related points to the possibility of rounded stones imbedded in ancient strata having sometimes had a different origin. I think it is also possible to conceive an instance in which the position of such stones relatively to contiguous beds, not easily explained on the usual supposition of their being waterworn fragments, might be accounted for by assigning to them an origin similar to that of the stones which I saw in the course of formation on the coast of Tenasserim.

Possibly, however, I have only been describing what has frequently been noticed before; though, if not-if what I have related should chance to be new-this trifling record may prove of interest, as indicating a plan of operation in Nature's great and multifarious workshop, which, I venture to think, would hardly be guessed at even by the most ingenious theorist. C. S. P. PARISH.

YOUR

THE EUPLECTELLA.

YOUR article on the Glass-rope Sponge (yalonema mirabilis of Gray), and the figure on p. 36, in the February number for 1872, called to my remembrance the account given me many years since by Mr. John Reeves, of Clapham, of the specimen of Glass-rope then in the East-India Company's museum. He stated that the specimen was the remnant of a stem of a Gorgonia, after maceration in acid by the natives of some island or coast in the Indian Ocean. When I first saw Euplectella speciosa, and observed the beard at its base, I was led to the conclusion that this was also a preparation from a spongoid animal, bleached probably by immersion in water, during which process the ova of crabs had passed through the meshes, and became slowly the mature animals that one sees inside Euplectella. Lately, in looking through Esper's work on corals, to find a figure of that coral-like Gorgonia of which Mr. Reeves had spoken, I was arrested by the plate in vol. iv.,

Fig. 118. Portion of ditto, magnified. ::

"Net-shaped Tubularia. - In this sea-product, the organic construction of the animal is not sufficient to decide the way of growth and vessels of nourishment. The net-formed cavities come nearer the sponges; but it has a shining substance, and softens in water, and the web of this is of quite different construction. It consists partly of strong threads, partly of leafy gills. It cannot be the dwelling of some foreign animal, for it is locked at the largest end.