I have thrown together, in this chapter, the ores of several members of a family of the elements, which may be called the family of the magnetics;* and I have also, from its frequent chemical association with iron, placed titanium along with them. No attempt was made by me to analyse the ordinarily-employed iron ores, but only such as, from their apparent purity, or from the excellence of the specimens, appeared to be of mineralogical interest.

“If the n roots of the equation

“are all real, then all the roots of the equations

“and

“are also real, and one of the n—1 roots of the latter lies between each adjacent “two roots of the former.”

Two specimens of the worm which forms the subject of this memoir were brought to Professor Moseley, in 1872, by a coolie trained for the purposes of collecting by Dr. Thwaites, F.R.S., the distinguished curator of the Peradeniya Gardens at Kandy; each was found at the bottom of a deep burrow, in company with a single egg-case, in the neighbourhood of that town. Professor Moseley entrusted me with them for study and description, and I have to thank him for much valuable assistance during the course of my work, which was carried on in the Oxford Natural History Museum.

I have again been privileged by Professor A. Geikie, Director-General of the Geological Survey of Great Britain and Ireland, in being allowed to bring before this Society the results of a further study of the Crustacea and Arachnida obtained by the Geological Survey from the Lower Carboniferous rocks of the Scottish Border. Since my former papers on those subjects were read, a considerable amount of fresh material has come to light, which has allowed of many species, which were formerly represented by fragmentary specimens, to be more fully described, and several altogether new to science to be added to our former list.

Through the kindness of Dr. A. Geikie, Director-General of the Geological Survey of Great Britain, I have had the pleasure of examining the fossil plants collected by the Scottish Geological Survey from the Calciferous Sandstones of Eskdale and Liddesdale.

I was led to the following investigations while seeking an elementary, and at the same time instructive, application of Hamilton's General Method in Optics. They were completed in all but a few of their numerical details before I met with the remarkable paper by Wollaston, in which the subject of multiple atmospheric images seems first to have been treated by a sound physical method. Wollaston's experiment with a long bar of iron raised to a high temperature suggests undoubtedly the true explanation of at least many of the curious phenomena seen by Vince, Scoresby, and others. But he seems to have thought that sufficient temperature-differences for the natural production of the phenomena could not exist in the atmosphere; and thus the latter part of his paper, in which he tries to explain them by the agency of aqueous vapour, presents a singular contrast to the strength and correctness of the earlier part. A good deal of what follows is implied, if not directly stated, in Wollaston's paper; but I think there is sufficient novelty in what remains to justify my bringing it before the Society.

The area lying between the north of Britain and the Faeröe Islands is classical in the annals of Marine Zoology, not only from the fact that the first systematic deep-sea investigations undertaken by this country were carried out there, but also from the number of new and remarkable types of animal life which have been first found in that region. Speaking only of the Echinoderm fauna, in justification of these remarks, it will suffice to mention the discovery of such forms as Phormosoma and Porocidaris amongst Echinoids, and of Hymenaster, Korethraster and Zoroaster amongst Asteroids.

In the present paper I propose extending my previous observations “On the Structure and Division of the Vegetable Cell.” I have shown that a nucleolus and nucleolo-nucleus (at Professor Rutherford's suggestion I now propose terming this the endonucleolus) are essential, and in most cases evident, parts of every growing vegetable cell, and that the division of the endonucleolus very probably precedes that of the nucleolus, just as division of the latter undoubtedly precedes that of the nucleus, in all the cases investigated.