for hours I could trace no co-ordination between the movements of the stems and those of the tentacles. They were not directed to a common object of catching food, and if the Pedicellina; like other polyzoa, possess a "colonial nervous system," they have no brain capable of directing their whole mechanism to an intelligently devised end.

The whole class of polyzoa possess, so far as I have observed them, very restless stomachs, and in the Pedicellina the particles of food were not suffered to be a moment at rest, but were spun round and round by the constant action of the cilia with which the digestive tube is lined. In the pursedup individual to the left of the engraving, the dark mass appeared to consist of the remains of a feast, ready to be turned

60X

out of doors, while the lighter mass below it, still under process of digestion, performed the circumtwistatory movement imparted to a leg of mutton by a roasting-jack. In some other Polyzoa, as the Plumatella, the food is tossed backwards and forwards up and down the digestive tube.

In the sketch some of the stalks are without heads, or more properly bodies, and on this subject Johnston observes* that, "like the hydroid Tubularinæ, the life of the body is of shorter duration than that of the stalks, the former fading or falling off, when a new one is reproduced in its place." He likewise cites Professor Reid to the following effect:-"A few days before this (the falling off of the body) takes place, the tentacula are permanently bent inwards, and the membrane surrounding their lower parts remains contracted, so as to completely, or nearly completely, cover the upper surface of the body, presenting, in fact, the appearance which the animal temporarily assumes when disturbed. The body then becomes more opaque, and at last falls off. When this has taken place the stalk retains its property of alternately contracting and relaxing its different surfaces at intervals, upon which its movements depend. After the lapse of a few days the top of the stalk enlarges, and a minute head presents itself, in which the different parts of the body are developed." This is an interesting fact when it is considered that the body contains the mouth, stomach, and other important organs, and also the nervous ganglion which performs the functions of a restricted brain. It is an instance of the power of the colonial life which animates every member of a polyzoan group in addition to what we may term his individual life, and is evidently a process of the same character as that which forms the original offshoots from the parent stem. Inside the mouth cavity, and below the tentacles, ciliary action may be observed, and favourable specimens display the circular band of muscles running round the margin of the cup, whose function is to pull it together.

Professor Allman discovered an arrangement of the tentacular disk which approaches these creatures to the Hippocrepian Polyzoa, that is to those in which the tentacles are arranged not in a circular, but in a horse-shoe group. Three species may be found on our coasts: the P. echinata, just described, with spines on its stalks; the P. gracilis, which has stalks smooth, thin, and long; and the P. Belgica, with smooth stalks inflated about the middle. The stalks rise from a creeping shoot, and the creatures are commonly found parasitic on corallines and sea-weeds, between tide marks, but especially near low-water mark. The species mentioned above vary in

* A History of British Zoophytes, by George Johnston, M.D., LL.D. Second edition, p. 384.

the number of their tentacles. P. Belgica has twelve tentacles, gracilis and echinata about twenty. Some of my specimens of P. echinata had eighteen.

In Mr. Gosse's Devonshire Coast he mentions an instance of a colony of P. Belgica growing as parasites upon the tail of a Syrinx, a wandering animal of vermicular shape belonging to the Echinodermata, and, as might have been supposed, an unfit site on which to found a colony of Polyzoa.

Many other objects of interest rewarded a little pains taken at Llandudno, but I will only allude to one of them, the Perophora, just for the sake of mentioning a rapid change in transparency which a short period produced in this interesting mollusk, without its showing any other symptom of bad health. One afternoon Mr. Drabble brought in a group of Perophora to show the beautiful ciliary action of its internal gills, which he had been admiring under his own microscope shortly before. On trying it with mine our success was very moderate, and no mode of illumination would make it sufficiently clear. For experiment sake he fetched his own instrument, but the result was the same, the explanation being that the outer skin of the animal had contracted, or undergone some other change, and its translucency was impaired.

Some of my readers may find themselves at Llandudno, and the preceding remarks may help them to collect objects; but most that I have said will apply to other sea-side places, and none can be found in which nothing of interest for the microscopic naturalist exists. My Welsh trip left many pleasing recollections, but there is a peculiar charm in marine zoology, and while the outlines of hills and mountains often rise in my view, I see with equal clearness of remembrance the motions of the Pedicellina, or the brilliant lightning sparks emitted by irritated colonies of Sertularia newly dredged from their homes at the bottom of the bay.

ON CAMPHOR PULSATIONS.

BY CHARLES TOMLINSON,

Lecturer on Physical Science, King's College School, London. [We have much pleasure in publishing the following interesting letter from Mr. Tomlinson, who is quite right in stating that the article in our May number to which he refers did not detail all the precautions necessary for the successful performance of the more delicate experiments. Our object was rather to call attention to his very good and accessible book than to supply a substitute for it. We are glad to hear that the further investigation of the "Storm Glass" occupies his attention.]

In the INTELLECTUAL OBSERVER for May last you notice briefly a few experiments from my small volume recently published, entitled Experimental Essays; so briefly, indeed, that should your readers endeavour to repeat them they may fail of success through not taking all the precautions which I have detailed in my book. For example, the experiment for exhibiting the camphor currents is one that requires great care, and several favourable conditions to make it succeed. In the first place, the vessel must be quite clean; secondly, the water must be quite clean,-it need not be distilled; thirdly, the camphor must be cut into the form of a stick, or a three or four-sided prism, and be mounted in forceps, as shown in the engravings on page 38 of my book; fourthly, the surface of the water must be very faintly dusted with lycopodium powder, which is best done by tying a small quantity of it up in a muslin bag, and gently shaking it over the surface; fifthly, the day must be fine and dry. If all these conditions be observed the experiment will succeed. As soon as the camphor is lowered into the water a powerful repulsion of the lycopodium powder takes place, occasioned by the formation of a camphor film, from which lines of solution will stream out, and, being reflected symmetrically by the side of the vessel, will throw the lycopodium powder into pairs of revolving wheels, and the action will continue with greater or less vigour so long as the camphor continues to be immersed, provided the air be sufficiently dry to get rid of the film by evaporation. In the course of some hours, depending on the size of the camphor stick, the camphor will be cut across at the surface of the water (as in Venturi's experiment, described in my first essay), and the lower portion thus becoming detached will rotate about the surface of the water and destroy the symmetry of the lycopodium wheels. On removing this piece, and lowering the stick so as to dip just below the surface of the water, the currents will set in afresh, and a new incision be made in the camphor. In this way I have kept up these currents for fifty or sixty hours.

VOL. IV.-NO. I.

C

The vessel selected for the above experiment was a conical foot glass, four inches in diameter at the mouth. I have lately had occasion to show the experiment in a very shallow vessel with a flat bottom, and have obtained some additional results, which may be interesting to your readers. Two vessels were employed, one a glass saucer, used for holding a glass flower pot; it is five inches in diameter, and slightly raised at the bottom. The other a flat dessert dish of uncut glass, 6 inches in diameter. The phenomena are best seen in glass vessels, but a dinner or dessert plate will answer the purpose. The glass saucer was made quite clean, two ounces of water were poured into it, and a stick of camphor, 1 inch long, and about 4inch square, with a square base, mounted in forceps, was brought down so as to touch the bottom in the centre of the slightly convex swelling. No sooner does the camphor touch the water than a series of vibrations sets in, agitating the whole surface of the water with rapid pulsations, so rapid, indeed, that it is scarcely possible to count them. I have, however, made out as many as 260 per minute.* In this small quantity of water solution takes place rapidly, and the water becomes saturated; hence the pulsations gradually diminish to 60 or 80 beats per minute, when solution and evaporation may be considered as pretty well balancing each other. I have even known the pulsations to sink down to 8 or 10 per minute, and to subside altogether when the air became damp from wet weather. On changing. the water the pulsations will set in again, but not with the maximum rapidity, unless in a dry air.

There is one condition connected with the complete success of this experiment which I was some time in discovering. It is this. The stick of camphor must be cut in the direction of the grain or cleavage of the camphor, but not across it or obliquely to it. On holding a piece of camphor up to the light it will soon be seen in what direction the cut is to be made, and when the piece has been nicely trimmed and mounted in its forceps, and brought down so as to touch the bottom of the vessel, the action appears to be this:-The water rises by capillary attraction some way up the camphor, and detaches a portion of its substance, which is then spread out in the form of a film over the surface of the water by the attraction of adhesion, and is there disposed of by solution and evaporation, after the manner of essential oils. As the film is being detached, it repels the water from the camphor, and produces a depression of surface all round the stick; the water recovers itself by a bound, capillarity again comes into play, another film is detached, and matters proceed as before; the result being a series These rapid pulsations are best seen on the larger surface of the water in the dessert dish.