matrix. Dilute acetic acid rapidly dissolves all but the finest and some of the coarsest granules, but apparently has no effect on the creature. Moderately strong solution of caustic soda causes the matrix to swell up. The granules are little affected by weak alkalies, but are dissolved by strong solutions of caustic soda or potash."

Professor Huxley thus describes the varieties of Coccoliths he calls "Discoliths" and "Cyatholiths," the former being "oval discoidal bodies with a thick refracting rim, and a thinner central portion, the greater part of which is occupied by a slightly opaque, as it were, cloud-like patch." These bodies are between 1-4,000" and 1-5,000" in long diameter, but may be found 1-2,700′′ or 1-11,000′′. The Cyatholiths are described as "oval, convex on one face, and flat or concave on the other." When lying flat they" appear composed of two concentric zones, surrounding a central corpuscle." Size from about 1-1,000" to 1-8,000" in length.

To make what he conceives to be their structure more clear, Professor Huxley says, "supposing it (a Cyatholith) to rest upon its curved surface, it consists of a lower plate, shaped like a deep saucer or watch-glass; of an upper plate which is sometimes flat, sometimes more or less watch-glass shaped; of the oval thickwalled, flattened corpuscle, which connects the centre of the two plates, and of an intermediate substance, which is closely connected with the under surface of the upper plate, or more or less fills up the interval between the two plates, and often has a coarsely granulated margin. The upper plate always has a less diameter than the lower, and is not wider than the intermediate substance. . Suppose a couple of watch-glasses, one rather smaller and much flatter than the other; turn the convex side of the former and the concave side of the latter, interpose between the two a hollow spheroid of wax, and press them together-these will represent the upper and lower plates and the central corpuscle. Then pour some plaster of Paris into the interval left between the watch-glasses and that will take the place of the intermediate substance." The sketches attached to this description represents the Cyatholiths as very much like shirt studs, the front piece being either a simple curve or flat.

I suppose the objects which I have found in abundance in the deep sea mud, which Dr. Carpenter obligingly furnished me with, are "Cyatholiths," and if so I think they will be found still more complicated than they are represented in the preceding account. examined them with various powers, Ross's inch, Beck's and,

I

and Ross's ths condenser. Ordinary transparent illumination is very unreliable when the forms of minute objects of considerable refracting power have to be ascertained. I tried therefore to view them by reflected light, but only with partial success. The best information seemed to result from the use of Ross's inch, stopped down to a moderate angle (I believe about 70), and his D eye-piece, giving a power of 420 linear. The illumination was arranged with the largest hole and central stop of his ths condenser, which strongly light up the object upon a dark ground. By varying the angle of the mirror under the stage, the principal light can be thrown from any azimuth, and strong shadows cast in the opposite direction. If different sides are successively lit up in this way the various hollows become conspicuous, and effects are produced similar to the views obtained of lunar craters when the sun is rising or setting upon them. In numerous instances I have obtained the appearance shown in Fig. 1 d. First there is an outer rim, slightly raised, then a shield, or dishcover-like elevation, and in its centre a depression with one or more bright dense spots rising in it. As these objects are anything but easy to make out, I shall be glad to know what other observers can see.

Professor Huxley names the protoplasmic matter which makes the sea mud viscid, Bathybium, thereby assuming its being a distinct organism, which may not be the case. The varieties of Coccoliths which he names "Discoliths " and " Cyatholiths," he is led to believe "are not independent organisms, but stand in the same relation to the protoplasm of Bathybium as the spicula of sponges, or of radiolaria, do to the soft part of those animals."

This seems a very doubtful hypothesis. Its foundation is apparently the absence of any marked quantity of sarcode in the Coccoliths, as evidenced by their prompt disappearance in dilute acetic acid. It is very advisable, however, that observations should be made on these bodies in a living state, as soon as they are obtained by dredging.

The Coccospheres which I have examined in Dr. Carpenter's dredgings are all small, when compared with free Coccoliths, and Dr. Wallich had noticed that free Coccoliths were usually much larger than any of those which were aggregated into Coccospheres. This suggests the notion that the bodies may grow after separation from the Coccospheres. Moreover, if we examine a number of Coccoliths with high powers, we shall find considerable difference in their details of structure, as well as in their size.

In the "Monthly Microscopical Journal for January, 1869,"