The study of a normal process in an organ so especially prone to disease as is the human uterus, is beset with many difficulties; so many foreign conditions are apt to be present, giving a false impression as to what this process really is. That this is the case to no small degree, when the character of the changes which occur in the normal involution of the uterus after child-birth is the subject of observation, is shown by the variety of opinions held and stated by doubtlessly competent observers; for while one holds that the muscle undergoes a fatty degeneration, another holds that no such fatty change occurs; while one asserts that only a certain number of the fibres degenerate and disappear, another states that so complete is the destruction, that not one single fibre present in the uterus before birth survives the process; while another goes to the extent of saying, that the puerperal uterus can in no way be distinguished from a uterus that has undergone an inflammatory process.

In a former paper I described certain experiments on the relations of magnetism and twist in iron and nickel, the chief results of which it may be well to give briefly here. When an iron or nickel wire is under the influence of longitudinal and circular magnetisations, it twists in a direction which is definitely related to the direction of the magnetising forces. This effect in iron was discovered by Wiedemann, and for convenience I shall call it the Wiedemann Effect. It was pointed out by Clerk Maxwell that the Wiedemann effect might be explained as a consequence of the earlier discovery made by Joule, that iron lengthens in the direction of magnetisation, and contracts at right angles thereto. Led by a consideration of Barrett's discovery of the shortening of nickel wire in the direction of magnetisation, I determined to test nickel in the same way in which Wiedemann had tested iron. It was quite obvious that, if Maxwell's explanation of the Wiedemann effect were the true one, nickel wire should, ceteris paribus, twist in a sense opposite to that in which iron twists. The experiment when made completely fulfilled the expectation. Thus, when an iron wire, with one end fixed, is traversed by an electric current in the direction in which it is at the same time longitudinally magnetised, the wire is twisted so that the free end rotates right-handedly with reference to the traversing current, or the longitudinal magnetisation. In nickel, on the contrary, the corresponding rotation is left-handed. This was the chief conclusion arrived at in my earlier paper; and a little consideration will show how very readily the Wiedemann effect, whether in iron or in nickel, is explained in terms of the simpler strains studied by Joule and Barrett.

A copy of Mr Marrat's paper “On the Fossil Ferns in the Ravenhead Collection” having come into my hands, I was led to visit the Liverpool Free Public Museum in 1886, and again in 1887, with the object of examining this interesting collection, and while doing so I received every assistance from Mr Thomas J. Moore, the Curator, and Mr F. P. Marrat, to whom I take this opportunity of expressing my indebtedness for the many kindnesses I received while studying the Ravenhead plants. I have further the pleasure of acknowledging the privilege accorded me by the Museum Committee, through the kind offices of the Rev. H. H. Higgins, which allowed me to have a number of specimens sent to Stirling, where I could more advantageously examine them than in the Museum, where the literature of the subject is limited.

Teilia Quarry, from which the fossils described in this paper have been collected, is situated about a quarter of a mile north-east of the village of Gwaenysgor, which is distant about five miles from Rhyl and one from Prestatyn.

The geology of the district has been fully described by Mr G. H. Morton, F.G.S., from whose paper the following notes are compiled:—

A considerable part of North Flintshire is occupied by a great development of limestone, which is generally referred to in writings on the subject as “Carboniferous Limestone.” It forms a tract of hilly ground, some of the higher points rising to a height of over 800 feet. These limestones lie immediately beneath the Cefn-y-Fedw sandstones, and occupy a hollow of considerable extent in Silurian strata.

The fragmentary nature of our knowledge of the behaviour of the more strongly basilous hydrates and carbonates at high temperatures is owing chiefly to the absence of a suitable material for the necessary crucibles. Unfortunately there is no metal which combines the infusibility of platinum with the chemical inertness of gold, in opposition to fiery-fluid caustic alkalies. But the corrosive action of these on platinum, as I showed some years ago, is a function only of the peroxides formed from them by the action of atmospheric oxygen, and, consequently, can easily be prevented by operating in an atmosphere of hydrogen or nitrogen.

In a former paper (Trans. Roy. Soc. Edin., vol. xxxiii. part ii. p. 465) the ellipsoid under consideration was supposed to have its three axes different from one another in length. I consider now the more simpler case of an Ellipsoid of Revolution. The same notations as in the former paper shall be made use of, and for the establishment of some of the results which form the basis of the present paper, reference must be made to the former.

Excepting the few species noticed in the Report on the Ostracoda of the “Challenger” Expedition, scarcely anything, so far as I know, has been published respecting the Ostracoda of the South Sea Islands. Prof. G. M. Thomson has indeed published in the Transactions of the New Zealand Institute (1878), a paper on Crustacea, which includes a few marine and fresh-water Ostracoda of New Zealand; and the Rev. R. L. King, in the Proceedings of the Royal Society of Van Diemen's Land (1855), described numerous species of Entomostraca, amongst which were several fresh-water, but no marine, Ostracoda. Dr Baird also published a species of Cypridina from New Zealand. I have myself contributed to the Proceedings of the Zoological Society of London (1886) a paper on Entomostraca collected in South Australia, chiefly by Professor Ralph Tate of Adelaide, including a considerable number of fresh-water Ostracoda; and in a French publication (Les Fonds de la Mer), edited by the Marquis de Folin, there are likewise, by myself, descriptions of a few species taken at Nouméa, New Caledonia. There are also, in a paper of mine published in the Transactions of the Zoological Society (1865), notes of a few Australian marine species. This, I think, represents the sum of our present knowledge respecting the Ostracoda of these regions.

The phosphines which have been obtained as yet are not very numerous, and with one or two exceptions their properties have not been exhaustively studied, a fact which is no doubt largely due to the difficulties encountered in preparing them in any quantity.

There are consequently a great many points in their history which require examination, and the object we had in view in the present investigation was chiefly to extend our knowledge of this interesting group of substances.

Some time since I received from Mr W. Smith of Ashburton, New Zealand, a single example of a worm belonging to the little known genus Phreoryctes, and published in the Annals and Magazine of Natural History for June 1888, a short account of the reproductive organs of this worm, for which I proposed the name of Phreoryctes Smithii.

More recently (November 1888) I have received, through the kindness of the same gentleman, a large number of specimens of the same species; the study of these enables me to offer to this Society a more complete account of the structure of Phreoryctes, which is at present very imperfectly known. It will be seen, however, that the present paper, though more extended, and dealing with organs to which little or no reference was made in my former paper, contains no important correction of facts stated in that paper. I have also appended (p. 638) a discussion of the systematic position and affinities of Phreoryctes.

Comparative anatomists have long desired detailed information on the placentation of the Sirenia. It is true that in 1878 Dr Paul Harting presented to the University of Utrecht a graduation thesis, in which he described the fœtal membranes and fœtus of a Dugong, which had been acquired a short time before for the Zoological Museum of that University. The specimen had been preserved for many years in spirit of wine, and had apparently been collected by a surgeon to a merchant ship. The fœtus was 27·8 centimetres (11 inches) long. The entire chorion, with the exception of the two poles and their immediate vicinity, was covered by densely packed, short and but little branched villi, and Dr Harting came to the conclusion that the placenta of the Dugong was diffuse and non-deciduate.

1. To complete the census of knots of any given order, that is, minimum number of crossings, it is necessary to include not only those in which the crossings are taken alternately over and under (Alternate ±), but also the Non-Alternate ±, those in which two or more consecutive crossings are alike over or alike under. Professor Tait has figured the forms of the alternate ± knots, of orders three to nine inclusive, on Pl. XLIV. vol. xxxii., Trans. Roy. Soc. Edin.; the object of this paper is to describe the non-alternate knots of these orders.