ii8 



A^A TURE 



[November 25, 1909 



number, and thus considerably outnumber the parts of a 

 typical flower (twenty-four, including bracteoles). The tip 

 of the bud was always damaged, but in many a shrivelled 

 pistil was present, and sometimes below this semi- 

 foliaceous stamens were found. The specimen is of interest 

 as resembling a teratological form of Erica cinerea de- 

 scribed by Maxime Cornu in 1879. — Prof. H. H. W. 

 Pearson : Types of the vegetation of Bushmanland, 

 Namaqualand, Damaraland, and South Angola (a pre- 

 liminary report of the Percy Sladen Memorial Expedition 

 in .South-west Africa, 1908-9). The floras of the regions 

 named in the title are distinctly related if the vegetation 

 found on the Huilla plateau in South Angola be excluded. 

 Otherwise tTie differences that are observed are to be 

 accounted for mainly as a result of differences of (i) 

 elevation ; (2) atmospheric humidity ; (3) depth at which 

 permanent supplies of underground water are available ; 

 (4) geographical position. In all the rainfall is scanty 

 and inconstant, and there is a prolonged drought in the 

 winter season. Near the coast, in some places up to 

 elevations as great as 2700 feet, the total annual rainfall 

 is never more than a few millimetres, and frequently fails 

 altogether. The affinities of these floras are with' those 

 of the South Central .Xfricnn highlands. In South Angola 

 many species are derived undoubtedly from the coast and 

 Montane regions of West Tropical Africa. Throughout, 

 the vegetation is xcrophytic in character, and is marked 

 either by a short period of duration or by the possession 

 of those structural peculiarities which are found in dry 

 climate perennials. Of these, hairiness is not a con- 

 spicuous feature ; except in Lower Namaqualand, succu- 

 lence is not common. A round, bushy habit is marked 

 throughout. The root system is deep ; the leaves are 

 simple and of small size, and with a strongly developed 

 cuticle. The formations and associations indicated are pre- 

 dominant by reason either of their great extent or of 

 striking peculiarities of the plants composing them. They 

 are arranged in the main geographicallv from south to 

 noi-th. 



Zoological Society. November 9.— Dr. S. F. Harmer, 

 F.R.S., vice-president, in the chair. — Sir H. H. Howorth : 



Some living shells, their recent biology, and the light they 

 throw on the latest physical changes in the earth, i., 

 Mya arcnaria. The author stated that the Mya arenaria 

 or clam is widely distributed in the North Boreal, Euro- 

 pean, and North American seas, and claimed to prove 

 that it is a recent migrant into the former, and has prob- 

 ably not been there more than 300 years. The notion that 

 it is an Arctic shell is a mistake. In the Arctic lists Mya 

 truncata, var. oblonga. has been mistaken for it, and the 

 glacial character of the beds in which it has occurred, 

 which has been postulated from its occurrence there, has 

 accordingly been a wrong inference. Brogger has argued 

 that it migrated from America. It was abundant in the 

 Crag seas, and occurs in derivative fragments in the Drift- 

 beds, but it does not occur in the estuarine deposits or 

 raised beaches, proving that after the period of the Crag 

 it became extinct in Europe, and has since been re-intro- 

 duced. He regarded the cause of its extinction as a 

 mystery, since the group of estuarine shells with which it 

 is found has lived continuously in Europe since later Crag 

 times.— C. Tate Regran : The Asiatic fishes of the family 

 AnabantidEE (including the Osphromenida?). The author re- 

 marked that the order Labyrinthici was an isolated and 

 termmal group, probably derived from a cyprinodontoid 

 stock, and that it comprised two suborders, Ophio- 

 cephaloidei and Anabantoidei, the latter including the 

 families Anabantidae and Luciocephalida;. The fndian 

 element in the fresh-water fish-fauna of Celebes, including 

 two labyrinthic fishes, was shown to consist of (i) species 

 which had travelled by sea, and (2) species which had 

 probably been introduced by man. The great importance 

 of Wallace's line for fresh-water fishes was thus vindi- 

 cated. The Asiatic genera and species of Anabantida; were 

 described, including several new forms of Betta and 

 Trrchopodus, and the Asiatic genus Anabas waq shown to 

 differ markedly from the African Ctenopoma and Spiro- 

 branchus,— J. Lewis Bonhote : Some mammals brought 

 home from Egvpt. The oaper dealt with about twentv- 

 pight species, chiefly small rodents, and the main points 

 of interest were the recognition of Procavia burton!, the 

 NO. 2091, VOL. 82] 



Egyptian hyrax, as a valid species, the re-discovery of 

 Acomys russatus, hitherto only known from Palestine, and 

 the description of a small species of Dipodillus, the last 

 two species having been taken on the Mokattam Hills 

 within three miles of Cairo. 



Mathematical Society, Novemb-r 11. — Sir \V. D. 

 Niven, president, in the chair.— G. H. Hardy : (i) The 

 ordinal relations of the terms of a convergent 

 sequence; (2) the application to Dirichlet's series of 

 Borel's exponential method of summation ; (3) theorems 

 relating to the summability and convergence of 

 slowly oscillating series. — Prof. W. Esson : Notes on 

 synthetic geometry. — H. Bateman : Rummer's quartic 

 surface as a wave surface. — Prof. H. S. Carslaw : The 

 Green's function in a wedge and other problems in the 

 conduction of heat. — J. L. S. Hatton : The envelope of a 

 line cut harmonically by two conies. — Rev. F. H. Jack- 

 son : A class of q-hypergeometric series. — Informal com- 

 inunications were made as follows : — Dr. E. W. Hobson : 

 An e.xtension of Abel's theorem concerning the sums of 

 series at points on the circle of convergence to oscillatory 

 series. — Prof. A. E. H. Love : The effect of the earth's 

 rotation upon the observed values of the lunar disturbance 

 of gravity. 



Cambridge. 



Philosophical Society. October 25. — Dr. Hobson, vice- 

 president, in the chair. — A. A. Robb : Discussion of a 

 difference equation relating to the tension of overhead 

 wires supported by equidistant poles. — F. G. Sinclair ; 

 Note on the abnormal pair of appendages in Lithobius. — 

 J. E. Littiewood : A class of integral functions. — J. A. 

 Crowther : The scattering of the rays from radium by 

 air. — R. Whiddington : Note on the electrical behaviour 

 of fluorescing iodine vapour. The note describes an ex- 

 periment showing that iodine vapour is un-ionised when 

 brilliantly fluorescing under the action of the arc light. — 

 Rev. H. J. Sharpe : The reflection of sound at a para- 

 boloid. — G. W. C. Kaye : The emission of Rbntgen rays 

 from thin metallic sheets. Thin metal leaf antikathodes 

 were subjected to bombardment by kathode rays, and the 

 (emergent) X-rays proceeding from the remote side of the 

 leaf were compared with those which left on the near side 

 (incident). In general, the emergent Rbntgen radiation in 

 such cases exceeds the incident in intensity, markedly so 

 in the case of aluminium. The ratio of the emergent 

 intensity to the incident increases with the speed of the 

 kathode rays employed. As the thickness of the meta! 

 leaf is increased, the emergent intensity increases to a 

 maximum and then dies away, the incident intensity mean- 

 while gradually increasing to a constant value.— F. 

 Norton : The emission of positive rays from heated phos- 

 phorus compounds. 



November S. — Prof. Bateson, F.R.S., president, in the 

 chair. — N. R. Campbell : Discontinuities in light emission. 

 An account is given of an attempt to test the theories of 

 Sir J. J. Thomson and of Planck as to the atomic nature 

 of radiation by means of observations on the fluctuations 

 in the intensity of a source of light. The experiments are 

 similar in nature to those of Meyer and Regener, based 

 on the theory of von Schweidler, on the fluctuations of an 

 ionisation current due to the a rays of radium. The 

 theory and the methods of the experiments are discussed 

 at length, and also the nature and cause of an unexpected 

 difficulty which has prevented, up to the present time, the 

 attainment of definite results ; but it is hoped that such 

 results may be reached in the near future. — J. A. Orang^e : 

 The shape of beams of canal rays. An appendix to a 

 paper previously communicated to the society. In that 

 paper it was suggested that the component rays in a beam 

 of canal rays are straight, the curved boundaries of the 

 beam being envelopes merely. This appendix describes one 

 or two simple experiments whrch support that view. — 

 H. Bateman : The determination of solutions of the equa- 

 tion of wave rnotion which involve an arbitrary function 

 of three variables which satisfies a partial differentia! 

 equation. — H. J. Priestley : The oscillations of superposed 

 fluids. — L. B. Turner : The stresses in a thick hollow 

 cylinder subjected to internal pressure. — Sir J. J. 

 Thomson : The theory of the motion of a charged particle 

 through a gas. It is pointed out in this paper that, in 

 consequence of the "persistence of velocities," which i=- 



