The structures known as pedicellariæ were first described by O. F. Müller. He regarded them as parasitic organisms, and described under the generic name of Pedicellaria three species—Pedicellaria tridens, P. triphylla, and P. globifera. Lamarck, in the first edition of his “Animaux sans Vertèbres,” published in 1801, and also in the second edition, following Müller, classified the genus Pedicellaria with the Corynidæ and Hydridæ among the naked polyps. Cuvier also, in the first edition of the “Regne Animal,” took the same view of the nature of pedicellariæ. It was not until 1825 that the real nature of these organs was recognised. Delle Chiaje, in his work on invertebrate animals, asserted that pedicellariæ formed an integral portion of the Echinus, and were simply appendages of the test. The following quotation from his work shows that he thoroughly understood the true nature of these structures. He says (vol. ii. p. 324):—“Fanno elleno parte integrale degli echini e servon loro per attacarsi a corpi adiacenti ed anche a ritenere gli animaletti da cibarsi.”

In the progress of the Geological Survey of the South of Scotland, specimens referable to the genus Eoscorpius have been gradually accumulating. In 1876 J. Bennie, Fossil Collector to the Survey, obtained an example from the Coal-measures of Fife. Since then fragments have been disinterred by him and by A. Macconochie, also Fossil Collector to the Survey, from the Calciferous Sandstone series in the counties of Edinburgh, Berwick, Roxburgh, Dumfries, and Northumberland and Cumberland. It was not till the spring of last year (1880) that they began to be found in such a state as to necessitate a description of the fossils. In the summer of that year A. Macconochie obtained an almost entire example from the neighbourhood of Langholm, in Dumfriesshire. This year (1881) J. Bennie has secured several good though fragmentary specimens from the neighbourhood of Edinburgh, while A. Macconochie has sent in several from the counties of Berwick and Northumberland. In my capacity of Acting Palæontologist, I have had an opportunity of studying these remains, and by the permission of A. C. Ramsay, LL.D., F.R.S., Director General of the Geological Survey of Great Britain, and Professor A. Geikie, LL.D., F.R.S., Director of the Geological Survey of Scotland, I have been allowed to describe them.

In the following communication an account is given of some experiments made in the Physical Laboratory of the Glasgow University, whose object was the measurement of the change of conductivity produced by strain in a metal conductor.

Two constants are required in order to determine this alteration in the most general case of a homogeneous isotropic conductor, strained in any way, as may be easily inferred from the analogy with elastic strains and stresses, constants expressing the change produced by uniform cubical compression and by simple distortion. The determination of the latter for brass is the object of the present paper.

I had added (at p. 140 of my paper on “Gaseous Spectra”) to the “small dispersion” account therein given of the above mentioned spectrum of luminous oxygen gas,—that two, if not four, of its very few and scanty lines appeared, when viewed with much higher dispersion, to be double; but that I hoped to give a more exact account of them, after completing some arrangements then in progress for increasing both the dispersion and magnifying power of my spectroscope.