one can become a good microscopical observer unless he is possessed of considerable manual dexterity, to be acquired only by long practice," and no work can be higher or more useful than that of assisting men to become original workers in any department of science.

Even the wide range of subjects over which our slides are spread tends to prevent the specialist from becoming too narrow, and to show him that there is an interest in pursuits other than his own. It is not at all desirable that we should imitate the coleopterist of Oliver Wendell Holmes. In our society he may learn much that has been previously done; the mission, though humble, should not be despised, for even as the known is the foundation of the unknown, so no original observer may or can safely disregard the studies of his predecessors.

I would now appeal to the members of the society to do all they can in the coming session to advance its interests by contributing interesting slides, adding to the slides notes, giving freely all their knowledge, either original or acquired. By so doing we shall attain in the future an even greater degree of prosperity than in the present.

Noctiluca Miliaris.

BY ALFRED W. GRIFFIN.

PLATE I.

THE

HERE is, perhaps, no one of the phosphorescent animals. yet known to science which possesses such highly luminous properties as the Noctiluca. To its presence in countless myriads upon the upper stratum of the water on calm summer nights is especially due that diffused form of phosphorescence, which is so essentially characteristic of temperate latitudes. Under the most favourable of these conditions the waves falling upon the shore leave, as they retreat, a glittering carpet of scintillating points, the oars of the passing boats seem to dip, as it were, in molten silver, while on the high seas the waste of waters churned

into foam by the revolving screw or paddles of the steamboat, leaves in its wake a broad luminous track, as far as the eye can reach. A glassful of water, taken from the surface of the sea at such times, at once reveals the cause of this wonderful phenomenon; for here and there will be seen floating minute bladderlike, transparent spheres. When irritated they at once respond by flashes of green silvery lights, and it is to this that the beautiful appearance already alluded to is due.

This description is from the pen of Professor Allman, who has studied the Noctiluca very closely in its various stages, and I venture to think he has under-rated rather than over-rated the brilliancy of the phosphorescence. It was my good fortune on a still moonlight night, last August, to be off the coast of North Devon, and for some time to witness the appearance of molten iron, which the paddles of the steamer caused as they churned up the water, illumined on its surface by myriads of these tiny lamps. The crests of the waves as they rippled against the shore were sparkling with light, defining their form in sharp outline, and all around the vessel the luminosity was most brilliant. The beauty of the scene led me to commence these investigations, which I have now the honour to place before the readers of this journal.

According to Suriray, Noctiluca Miliaris consists of a spherical, gelatinous mass, with a long filiform tentacle appendage, possessing an œsophagus, many stomachs, and ramifying ovaries. Huxley, however, describes the Noctiluca somewhat more explicitly, by first stating that it is about the sixtieth part of an inch in diameter, and next, that in appearance it closely resembles a peach—that is, one surface is a little excavated, whilst a groove runs from one side of the excavation half way up to the other pole. Where the stalk of the peach might be is a filiform tentacle equal in length to about the diameter of the body, which exhibits slow wavy motions when the creature is in full activity. The use of this appears to be chiefly to push away obstacles and as a motive power, and I venture to hazard the opinion that it is a greater sympathetic nerve communicating with lesser nerves, and thence to the luminous points at the apex of the body. If the water is agitated in which the Noctiluca is confined, or an

irritating substance like Ammonia be added, the tail, or tentacle is seen in rapid motion, and the light flashes out with great rapidity. This tentacle is extremely brittle, breaks with a short fracture, and is evidently composed of rings of spiral tissue. Dr. Webb states that he has never seen any restoration of this part should it be lost, and on the death of the creature it coils up; but I should add that even after the partial rupture of the investing membrane, and the discharge of its contents, he has seen it vibrating most vigorously. A very shallow cell in an ordinary glass slip is the most convenient method of examining the motions of this organ as it swims towards the under surface of the glass. The powerful uses for which this tail is employed require undoubtedly that it should be composed of strong muscular fibre. There is, however, a considerable measure of doubt as to whether or no there is any opening, or mouth, at its extremity.

The body itself is composed of a dense external membrane, continued on to the tentacle, and underlying this is a gelatinous membrane, throughout which minute granules are indiscriminately scattered. From this membrane arises a network of very delicate fibrils, possibly not more than one three-thousandth part of an inch in diameter, and these passing internally, become more open till they are merged into coarser fibrils, which converge toward the stomach and nucleus. All these are covered with granules, which are generally larger toward the centre. Quatrefages thinks that these granules move with the contraction and expansion of the membrane in which they are embedded. Supposing that we are viewing the animal in front, the oral aperture will be found on the right side of the groove, a little distance below the tentacle, which is on the left. This mouth-like organ appears in the character of a short oval tube, consisting most probably of striated muscular fibre, leading into the granular mass of the alimentary canal, and from this latter the fibres and fibrils radiate. Near the point of insertion of this oral aperture there is always a mass of sand and other substances adhering with great tenacity to a semigranular material, with a hernia-like projection, and this substance is continued internally in much larger proportions. There appears to be an utter absence of anything like a digestive canal, but in the middle of this granular matter there are more frequently

vacuoles of more or less size, which have been considered by early writers, as Krohn and Suriray, to be veritable stomachs. These vacuoles are by no means synonymous with the shifting vacuoles of the Infusoria and Rhizopoda. Huxley's idea is that the oral cavity ends in a definite stomach capable of great dilation locally, and these dilations are connected by very narrow pedicles with the central cavity, such giving the appearance of "independent vacuoles." Brightwell's idea is that these "vacuoles," or vesicles, are temporary stomachs, or sacs, formed in the sarcode mass as they are required for the reception and digestion of food, and that they cease to exist after the food is digested. More recent investigations have shown that the food drawn into the mouth is received into the protoplasmic mass at the bottom of the oesophagus; extensions of this are formed which envelop the food with a filmy surrounding quite distinct from the protoplasmic mass. By this means we have "digestive vesicles" formed. These, however, soon pass into the arms of the central mass till they are surrounded completely by the protoplasm. The number of the vesicles vary from four to even twelve, and their place is subject to constant change through the movement of the substance in which they are embedded. The reticulations round the central mass are constantly changing, and thus the distribution of the nutrient material takes place as it finds its way into this network, through the walls of the digestive vesicles. Their contents are found to be principally Algæ and Diatoms. That singular diatom, Rhizosolenia styliformis, was found first of all in the Noctiluca, though it has been since seen floating in large masses on the surface of the sea; the chief form of Diatom, however, found in this Rhizopod is Actinocyclus undulatus. As the Noctiluca is so transparent, the form of the Diatom may be seen at a glance. After it has been in the vescicle for a few days it disappears altogether; probably the endochrome has been digested, and the siliceous frustule subsequently rejected.

The principal agent employed in conveying the food into the aperture, which does duty for a mouth, is a very delicate filament, or "flagellum," similar in character to a cilium, of the Rotifer type, which vibrates rapidly, and is as rapidly withdrawn inside. This band-like organ gradually narrows towards its extremity, and

its axis shows through its entire length transverse striæ. It seems to have the power of elevating its edges, so as to render one of its surfaces concave, and thus to form a tube-like process. This flagellum must not be confounded with the whip-like tentacle to which I have already referred, though there are some points of resemblance between the two: their position and difference in size form the great distinction.

As many, however, as fifty individuals may sometimes be examined without discovering this minute organ. The tail-like tentacle may be easily seen with a pocket-lens, whilst a quarterinch objective will be required to discern the cilium, or flagellum. Springing from the base of this tail-like appendage to the edge of the oral aperture is a ridge-like prominence, something in the shape of the letter S, apparently of a horny nature, and crowning this ridge is a tooth-like process, with three cusps, or divisions of unequal character. This tooth is one seven thousandth part of an inch high. Professor Huxley states that he has seen no movement in this organ; but another writer, Dr. Webb, throws some light on the subject by stating that he has seen the ridge contract, and that he has observed a backward and forward movement of the tooth as though working on an axis. It is easily broken, and becomes shrivelled up by the use of astringents.

With regard to an excretory aperture, sound observers have come to the conclusion that egesta are voided from the mouth, but the opinion of the few writers that we have upon this subject appears to be much divided. Just below this mouth-like aperture, or tube, there is a depression corresponding in shape, as I have said before, with an ordinary peach, and the base of this depression, which is funnel-shaped, appears to have some communication with one of the gastric pouches. Krohn states that he saw excrementa voided from the groove of the body, but he is unable to define the exact point. Huxley, though he has no precise data to go upon, thinks that from the general structure of the organism, a distinct anus must exist, and that the funnel-shaped communication must, therefore, serve that purpose.

From the rapid apparent change of shape which the Noctiluca presents whilst swimming about, and its continual alteration of position, it is by no means easy to get a clear and uninterrupted