Papers read to the Society, December 5, 1901.

I. “On the Spontaneous Ionisation of Gases.” By C. T. R. Wilson, F. R. S. II. “Notes on Quantitative Spectra of Beryllium.” By Professor W. N. Hartley, F. R. S. III. “Notes on the Development of Paludina with Special Reference to the Urino-genital Organs and Theories of Gasteropod Torsion. Preliminary Note.” By Miss I. M Drummond. Communicated by Professor Weldon, F. R. S. IV. “Preliminary Account of the Prothallium of Phylloglossum.” By Professor A. P. W. Thomas. Communicated by Prof. Howes, F. R. S.