A few years ago the late Sir C. Wyville Thomson gave me for examination some specimens of Ascidians which had been obtained during the cruises of the “Porcupine” and “Lightning,” and last summer I received from Mr John Murray the remainder of the Ascidiæ Simplices and two species of the Ascidiæ Compositæ from the same deep-sea dredging expeditions. Some additional specimens of the “Porcupine” Ascidiæ Compositæ have been placed in my hands during the last few days (January 1, 1884). The present paper contains a detailed account of the Simple Ascidians alone; the Compound forms will be worked up along with the “Challenger” Ascidiæ Compositæ, and will be described and figured in the second part of my Report upon the Tunicata of the “Challenger” Expedition. It may, however, be useful to state here that the “Porcupine” Compound Ascidians include:—

During the cruise of H.M.S. “ Triton ” a small but very interesting collection of Pycnogonids was made. Mr John Mueray sent it over to me, and asked me to prepare a report on it, which I gladly undertook to do.

After the Royal Society, Edinburgh, had been pleased in 1880 to accept and print my paper on the general appearance of Gaseous spectra as seen on a very small scale, but complete on that scale from one end to the other of the visible spectrum, I was desirous to present them with some very highly Dispersed and much magnified views of the more interesting and probably crucial portions of the most important of those spectra.

On a moonless night, whenever clouds of an ordinary elevation in the atmosphere appear upon, or pass across, the star-spangled sky behind them, they exhibit themselves, as a rule, dark, sometimes even black, in comparison therewith. And no wonder, when every part of the open sky from visible star to visible star therein must be lit up to some, though doubtless a very small, extent by the faintest general and cumulative radiance of those myriads and myriads of lesser stars, which only a large telescope can show to be individually existent as actual stellar points of light, but in their aggregate more nearly eternal, and still more constant from age to age, than our gigantic Sun itself.

If a row of n elements be taken, and closely following this array, but separated by a bar from it, we write n rows of n elements each; and closely following either outside column of this square array, but separated by a bar from it, we write n columns of n elements each; and closely following an outside row of this second square array, but separated by a bar from it, we write n rows of n elements each; and so on, passing from the rows or columns of one array to the columns or rows of the next, and ending not with a square array, but, as we began, with a single line of elements, we have the matrix representation of a bipartite function.

Of all known examples in physical science, of simplifying, and at the same time “precisionising” some of its fundamental data, which might otherwise fall to be entangled in high numbers, none has been happier than Fraunhofer's application of the letters of the alphabet to certain chief lines in the solar spectrum. Happy both in its conception by the inventor, and its universal acceptance since then by the world. Whence it comes to pass now, that in every country, whoever observes the solar spectrum at all, with whatever instrument, large or small, diffracting or refracting, and whether he holds to the undulatory, or any other theory of light, and catalogues spectral lines either in Wave-lengths or Wave-numbers, or merely in terms of the brass scale screwed to his instrument by a maker,—yet whenever he speaks of the line A, or B, or C, or any other so named by Fraunhofer, he singles out thereby from among thousands, exactly the same identical line which any and every other spectroscopist alludes to under the same simple letter.

Every spectroscopist is perfectly aware that the group of dark Fraunhofer lines in the Solar Spectrum, known as “ little b,” is composed of the biggest, broadest, most colossal lines in all the brighter part of any and every spectrum depending on Sunlight, whether direct from the Sun or reflected from the earth's atmosphere, the Moon, or any of the planets.

The dust particles floating in our atmosphere are every day demanding more and more attention. As our knowledge of these unseen particles increases, our interest deepens, and I might almost say gives place to anxiety, when we realise the vast importance these dust particles have on life, whether it be those inorganic ones so small as to be beyond the powers of the microscope, or those larger organic ones which float unseen through our atmosphere, and which, though invisible, are yet the messengers of sickness and of death to many—messengers far more real and certain than poet or painter has ever conceived.

The 119 subsolids (marked ss) and the 244 unsolids (marked us), of these unifilars are here arranged in lists according to their flaps. Fe is the number of flaps of e loops upon a knot; and the headings of the lists, as, e.g.10I, F2 = 1, F1 = 3, describe so far all the knots in the lists. Thus in 10I each has one 2-ple flap and three single ones. After the number in the list comes always the base on which the knot is constructed by the rules of my paper, XVII. in vol. xxxii. part ii. of the Trans. R. S. E.; and the reader who has that paper before him will find it easy to draw any knot on its base, nearly always there figured, by the first given flap, which is the leading one of the knot described; thus in 10I the first written flap is the double one, and in 10P, F3 = 1, F1 = 2, it is the triple one. The leading flap of a subsolid is always followed by a colon.

Having undertaken to continue the observations on the growth of trees commenced by my father in 1878, and carried on by him with unflagging zeal until a few months before his death in 1882, I give in the present paper the measurements made by him in 1881, which he did not live to publish, and those made in 1882 by myself. I shall also endeavour to point out the conclusions which may be drawn from the whole series of observations, beginning in 1878, arranging them under the heads of—

I. Annual Observations.

II. Monthly Observations.

III. Influence of Weather on the Growth of Wood.

The following additional remarks are the outcome of my study of the polyhedral data for tenfold knottiness, which I received from Mr Kirkman on the 26th of last January. My main object was, as in the first chapter of Part II., to determine the number of different types; as well as the number of essentially different forms which each type can assume, as distinguished from mere deformations due to the mode of projection.

This study has been a somewhat protracted one, in consequence (1) of the great number of tenfold knots; (2) of the very considerable number of distortions of several of the types, many of which are essentially distinct while others present themselves in pairs differing by mere reversion; and especially (3) of the fact that the polyhedral method often presents some of the distinct forms of one and the same type projected from essentially different points of view (of which, in the present case, there are sometimes twelve in all).

The Norway lobster, Nephrops norvegicus, on account of its abundance in the Firth of Forth, and the consequent ease with which it can be obtained from the Newhaven market, is given to the practical classes in the Natural History Laboratory of Edinburgh University for dissection, as an example of the decapodous Crustacea. One day in December last, while I was superintending the work of a class engaged in the study of this animal, one of the students, whose name I have unfortunately forgotten, called my attention to some globular protuberances on the intestine of the specimen he was dissecting. At the time I was unable to answer his questions any further than to say that the protuberances were the cysts of a parasite, and I put the specimen by for subsequent examination. On opening the cysts afterwards I found in them a small white worm, which proved to be a Trematode possessing novel characteristics. In the following paper I shall describe this parasite, and show that it is so distinct from all Trematodes hitherto known as to constitute a new genus. On several occasions I had the pleasure of examining the animal in the company of my friend and former colleague, Mr Duncan Matthews, and some of the points in its structure were first noticed by him.

A mechanism may be defined as a combination of plates, bars, or flexible members jointed together, so that, while the parts may move relatively to each other, the relative positions of all the different parts are determinate for each given possible relative position of any two parts.

It follows immediately that the simultaneous relative displacements, velocities, and accelerations of velocity of all parts are also strictly determinate.

This determination, by accurate graphic means, forms the subject of this paper. In it those mechanisms alone are considered that are composed of rigid members, the motions of whose parts are all continually parallel to one plane, the constancy of the plane being defined relatively to one of the members of the mechanism itself.

Introductory.—In the course of an inquiry into the physiological and therapeutical action of alkaline nitrites, and allied substances, I was struck with the strong resemblance which the action of nitroglycerine bears to that of the nitrites. The resemblance is, indeed, so well marked, that the action of the one may be held to be identical with that of the other, unless in respect of intensity. The suggestion, therefore, naturally occurred to me, that nitroglycerine is not a nitrate of glyceryl, as it is always represented, but a nitrite. For no ordinary nitrate, as an alkaline nitrate or nitrate of ethyl, nor any compound of glyceryl with another acid, as sulphuric acid, produces an action on the body at all resembling that of nitroglycerine. On referring to the various investigations which had been made for the purpose of ascertaining the chemical constitution of nitroglycerine, I found that none of them was sufficiently extended and exact to place beyond doubt its precise nature. The danger in manipulating so explosive a body had evidently prevented the various chemists from making a thorough examination of its composition. I at first thought that nitroglycerine might be a nitrite of glyceryl, having its nitrous acid so intimately combined with the glyceryl, that the acid did not exhibit its reactions when tested for in the usual way ; just as the acids of other ethereal compounds will not yield their usual reactions, unless special means are taken to forcibly dissociate the acid from the base ; for example, the acid of acetate of ethyl, or of chloride of ethyl. Certainly nitroglycerine gives no blue colour with a solution of starch and iodide of potassium and sulphuric acid, a very delicate test for the presence of nitrous acid. In order, however, to apply the test to the separated acid of nitroglycerine, I mixed an alcoholic solution of nitroglycerine with an alcoholic solution of pure caustic potash. The potash was ascertained to be free from nitrite, which I have frequently found present in small quantity in various specimens of ordinary potash. Decomposition of the nitroglycerine quickly occurred, and the fluid, when now tested for nitrous acid, was found to contain the acid in abundance, and so much of it, that for the moment I believed that nitroglycerine was, in reality, a nitrite of glyceryl; and hence the nature of its physiological action. Some estimations, however, of the quantity of the nitrous acid proved to me that whilst the larger portion of the nitrogen of the nitroglycerine appeared as nitrous acid in the decomposed products, yet a considerable portion was present in some other form.

1. By a knot of n crossings, I understand a reticulation of any number of meshes of two or more edges, whose summits, all tessaraces (ἀκή), are each a single crossing, as when you cross your forefingers straight or slightly curved, so as not to link them, and such meshes that every thread is either seen, when the projection of the knot with its n crossings and no more is drawn in double lines, or conceived by the reader of its course when drawn in single line, to pass alternately under and over the threads to which it comes at successive crossings.