OPHRYDIUM VERSATILE.

BY REV. W. HOUGHTON, M.A., F.L.S.

(With a Tinted Plate.)

A FEW remarks on this extremely interesting form of infusorial life may be acceptable to the readers of this magazine, many of whom, it is probable, have never been fortunate enough to see these bright green balls to which Ehrenberg has given the name of Ophrydium versatile. I find immense numbers of these balls in the clear water of a canal near my house, and should be happy to send specimens to any microscopic readers of the INTELLECTUAL OBSERVER, who may be particularly anxious to make the acquaintance of our versatile friend, provided such requests do not come in overwhelming numbers. At first sight an observer would be inclined to refer these vividly green masses to the vegetable kingdom; indeed, some years ago, botanists did claim them for their own, and gave the production in question the appropriate name (so far as external form is concerned) of Nostoc pruniforme; but no apple or green-gage plum is worthy, in point of colour, to be compared with good specimens of Ophrydium.

In Pritchard's last edition of the Infusoria (p. 598) Ophrydium is arranged with the genera Tintinnus, Vaginicola, and Cothurnia, and forms with them the family Ophrydina. This is Ehrenberg's arrangement, which, however, is very unsatisfactory. Stein and Dugardin refer the four genera just named to the Vorticellina group; it is, I think, impossible to study the characters of the individuals which belong to those genera, and not feel convinced that their true affinities are with that family.

There is very great difference of opinion with regard to the classification of the infusoria, and the various systems which have been proposed must, as Mr. J. Reay Green observes, "be regarded as premature, since we know so little of the life history of these animals that it is by no means improbable that many apparently distinct species are nothing more than transitional conditions of more adult forms." We may, however, I think, refer Ophrydium to the Vorticellina, without being very far from the mark. Fig. A represents a couple of Ophrydium balls attached to a piece of Anacharis alsinastrum. So far as I am aware one species alone of Ophrydium has been described, viz., O. versatile. It is thus characterized in Pritchard's Infusoria:"Body fusiform, tapering to a fine extremity from behind the middle, and anterior to it contracted into a cylindrical neck, supporting a funnel-shaped head, surmounted by an annular peristom, with a ciliated rotary disc. The mouth opens into a narrow

and long ciliated oesophagus. The contractile vesicle is seated near its end; the nucleus is long, narrow, and twisted. The external surface is thrown into close annular folds; and usually three longitudinal plaits extend from the posterior end as far as the middle of the body, which disappear when the body contracts. A subjacent cortical lamina is evident, and imbedded within this, numerous chlorophyll utricles, giving the animal a vivid green colour. When contracted, the body assumes the form of a long-necked flask, and even the nucleus shortens itself. In more complete contraction the figure becomes oval or globular. Fission is only longitudinal. When an Ophrydium quits its hold after fission, it swims away by means of a temporarily developed posterior wreath of cilia, just like a Vorticella. It is found encysted, and Stein believes in an acinetiform phase. Vividly green and associated in smooth and globular clusters or masses, which vary in size from a pea to a ball five inches in diameter; they are either free or attached. Ehrenberg states that in May, 1837, he saw hundreds of clusters as large as the fist, which, by the evolution of gas, were at intervals elevated to the surface, and driven by the wind to the edge of the water. In sea-water, also found by Brightwell, in fresh-water, and in a small turf pit, upon tendrils of roots of marsh plants, and the stalks of the white water-lily. Length of single animalcule stretched out, 1-120" to 1-90"."

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From this description it appears that Ophrydium versatile is an inhabitant both of fresh and salt water. I have never seen it in salt water, but have met with it in canals and ponds. It may be found throughout the whole of the year, and I have even obtained large specimens from water which had been frozen over; but in March and April the specimens appear to be most abundant, and the most beautiful both in form and colour. Fig. I represents a single individual magnified about 400 diam.; the parts referred to in the description given above are clearly visible. The animalcules are imbedded in a nearly colourless (not greenish," as Mr. Reay Green states) gelatinous substance; it is the animalcules themselves that give the green colour to the whole ball; they project their anterior extremities beyond the surface of the jelly-like mass, and are firmly attached to its substance by means of a very long non-contractile tail or peduncle, which breaks off from the body when the individuals take to a wandering mode of life. The gelatinous substance, which is homogeneous in nature, and not composed of numerous little cells as Ehrenberg has stated, is often slightly coloured with brown, which colour is caused by a parasite species of Alga that sends forth its long twisting filaments into the substance of the ball. The free animalcules, which are extremely lively little creatures, swim about by means of their anterior cilia,

and remind one forcibly of the Stentors, only that these latter are surrounded with cilia, while the free Ophrydia possess anterior cilia alone; in this respect they differ from the true Vorticella, which develope a posterior fringe of cilia before the individuals leave their spiral stalks. I have never seen anything like a posterior fringe of cilia belonging to a free Ophrydium, but have observed a peculiar minute setiform appendage at this extremity as represented in fig. C c.

If an Ophrydium ball be placed in a vessel of water, and be kept in a sitting-room, the animalcules in a few days will leave the gelatinous substance and swim freely about for a time, when they again attach themselves to the bottom and sides of the vessel in small radiating clusters (see fig. G), which, I believe, represents an early stage of globe-like growth. I have never seen the encysted state of an Ophrydium. In most of the infusoria are to be seen certain clear spaces of a circular form; these are termed "contractile vesicles," and "vacuoles." These are very readily observed in Ophrydium versatile. The "contractile vesicle" (fig. I d), which is supposed to be filled with some clear fluid, and which some suppose may serve the purpose of a rudimentary circulation, is situated in Ophrydium near the termination of the œsophagus, and dilates and contracts pretty regularly at intervals of eight or ten seconds; the "vacuoles" may readily be distinguished by their non-contracting and dilating properties. The "nucleus," which in Ophrydium is an elongated twisting band, and always filled with granular contents, may readily be observed by crushing an individual between two pieces of glass, when the solid "nucleus" will appear. It is now well known to microscopists that the so-called " nucleus " and "nucleolus" of the infusoria have been most satisfactorily proved to be the "ovary" and "testis," by the researches of M. Balbiani.

REFERENCES TO PLATE.-A. Ophrydium versatile attached to Anacharis alsinastrum. B. Portion of surface of ditto seen through lens. C. Free individual swimming by means of anterior cilia. D. Individuals in various forms. E. Granular contents escaping. F. In process of longitudinal division. G. Showing mode of increase. H. Filamentous alga. I. Individual Ophrydium magnified 400 diameters :-b, mouth surrounded with cilia; c, ciliated oesophagus; d, contractile vesicle; e, nucleus long and twisted; f, annular folds of external surface; g, longitudinal plaits; h, chlorophyll utricles; į, vacuole ; j, non-contractile peduncle.

ALLOTROPY.

BY W. B. TEGETMEIER.

THE singular phenomena which are known to chemists under the title of Allotropy are so remarkable, and can be so easily illustrated by means of a few simple experiments, capable of being performed without any particular apparatus, that they may advantageously form the subject of one of the series of practical papers that were commenced in a former volume of the INTELLECTUAL OBSERVER.

In

The term Allotropy is employed to signify the remarkable circumstance, that the same substance can exist in two or more totally different states, which are distinguished from each other by extraordinary variations both in their physical and chemical properties. The same substance, for instance, may be in one state fearfully poisonous, in another perfectly harmless. one condition it may be brittle, in another extremely elastic. Again, it may have a liquid and several solid states, being in one vitreous or glassy, in another crystalline, and in a third perfectly amorphous. These singular changes of condition are the more remarkable from the fact that any one may be produced at the will of the operator, each particular state being readily convertible into either of the others.

The most familiar examples of allotropic substances are the elements carbon, phosphorus, and sulphur. Of these the latter is most easily experimented upon, and as some new facts relating to its allotropic conditions have recently come to light, we will select it for illustrating this peculiar class of phe

nomena.

Common commercial sulphur, or that found native in several parts of the earth, is soluble in turpentine in most of the mineral oils, as benzine, and also in bisulphide of carbon; when crystallized, it exists in the form of elongated octohedrons. If a few pounds of the common sulphur be melted in a crucible and allowed to cool slowly until a crust forms on the surface (when the crust should be broken and the liquid exterior poured out), the sides of the cavity will be found to be lined with transparent yellowish needle-like crystals, having a totally distinct form from the octohedral variety, being in long oblique prisms. These crystals spontaneously change in the course of a few days and pass again into the first-named more opaque octohedral form, the crystals retaining their outward shape, but in reality being constructed of an aggregation of minute octohedrons.

This change from the transparent prismatic to the opaque octohedral form is one of great importance in the plastic arts. Sulphur, when melted at a low temperature, and first cast, pos

sesses a considerable degree of transparency, and a fair amount of tenacity and freedom from brittleness. It can be readily cut or trimmed with a knife, having very much the consistence of a hard horny cheese. Advantage is taken of this by the makers of plaster medallions and the copiers of old coins and medals. They moisten a plaster medallion, or grease slightly the surface of a medal, and then, securing a paper rim around it, pour on melted sulphur. This solidifies into the transparent prismatic variety, and may be cut and trimmed into shape, serving as a mould in which new plaster copies may be cast. After a few days, however, the sulphur resumes its octohedral brittle form, and the attempt to use it as a mould when in this condition generally results in its being defaced in consequence of its extreme brittleness.

Other peculiar allotropic forms of sulphur are produced by melting it at different temperatures.

When heated to a degree not exceeding 120 Cent., sulphur forms an exceedingly limpid mobile liquid, that possesses the property of taking sharper casts than any other substance, hence its employment as previously mentioned.

If it is heated to a higher temperature, it becomes gradually darker and extremely thick and viscid, so that the flask in which it is being melted may be inverted without its running out. The greatest degree of thickness and viscidity is attained at a heat of about 250° Cent. If it be heated to a higher degree it becomes more liquid again, though never to the same extent as when at a lower temperature. If in this highly heated state it is poured in a thin stream into water, sulphur assumes the extraordinary form of a rich amber brown transparent substance, possessed of a very high degree of elasticity and capable of being drawn out into threads. In this extraordinary condition it is quite insoluble in bisulphide of carbon and other menstrua that so freely dissolve octohedral or common sulphur.

In the course of a few hours, however, it returns to the common brittle condition, the change being accompanied by the evolution of heat, and, what is very remarkable, this change may be instantly brought about by placing the elastic sulphur in boiling water.

In the elastic state, sulphur is evidently in the vitreous or glassy form. This form is dependent on the fact that the sulphur has united with a proportion of heat, which has become latent in effecting this change.

A very good illustration of the vitreous condition assumed by some allotropic substances exists in barley sugar. This is formed by boiling sugar with the smallest possible quantity of water capable of dissolving it when aided by heat; as thus formed it is, whilst heated, a soft vitreous substance, capable of