142 



NATURE 



[December 8, 1904 



Entomological Society, November i6.— Frof. E. B. 

 Poulton, F.R.S., president, in the chair. — Mr. H. St. J. 

 Oonisthorpe exhibited the second recorded British speci- 

 men of Orchestes sparsiis, Fahr., talien by him on August 28 

 in the New Forest. — Mr. H. W. Andrews exhibited speci- 

 mens of Atherix crassipes. Mg., from the New Forest, the 

 only previously recorded locality in Britain being near 

 Ticehurst, Sussex. — Mr. G. O. Sloper exhibited aberrant 

 forms of Melitaea athalia from Luan, Switzerland, and 

 Martigny, in which the tendency of the black markings to 

 supersede the fulvous was particularly noticeable. — The 

 President exhibited cases containing Diptera, and a case 

 containing the skins of African Sphingid larvs, dried in 

 botanical paper, and after seventy years still preserving 

 their colours, from the Burchell collection in the Hope 

 Museum, Oxford. — Mr. C. O. Waterhouse exhibited a 

 gall of some lepidopterous insect found on the califate 

 bushes in Patagonia. The gall resembled that of Cynips 

 kollari, but was hollow, the walls being about | inch in 

 thickness. The circular door prepared by the larva was 

 about g inch in diameter. The pupa was lying free, with- 

 out any silk cocoon. It was suggested that the insect was 

 perhaps allied to Qicocecis. — Mr. G. H. Kenrick com- 

 municated a paper entitled " Natural Selection Applied to 

 a Concrete Case." — Mr. J. C. Kershaw communicated 

 papers on enemies of butterflies in south China, and a life- 

 history of Gerydus sinensis. — Mr. Nelson Annandale com- 

 municated a paper on the eggs and early stages of a 

 Coreid bug, probably Dalader acuticosta, with a note on 

 its hymenopterous parasites. 



Royal Microscopical Society, November 16. — Sir Ford 

 North, F.R.S., in the chair. — Mr. Hugh C. Ross exhibited 

 and described a new electric warm stage of his invention. — 

 Mr. C. L. Curties exhibited two new designs of the Nernst 

 lamp suitable for use with a current of 100 and 200 volts 

 respectively, adapted for use with the microscope, and fitted 

 with ground glass or blue glass fronts and mounted so as 

 to be used at any height or angle required. — A paper on 

 theories of microscopic vision, a vindication of the Abbe 

 theory, which contained some new views on the subject, 

 was read by Mr. Conrady. 



Linnean Society, November 17. — Prof. W. A. Herdman, 

 F.R.S., president, in the chair. — Mr. H. E. H. Smedley 

 exhibited forty-one models of Palseozoic seeds and cones. 

 The models of the seeds show the complexity of their internal 

 structure, whilst the models of the synthetically re-con- 

 structed calamitean and other cones display the high 

 organisation of the va.scular cryptogams of Palaeozoic times. 

 ■ — Note on the shape of the stems of plants : Lord Avebury. 

 The author pointed out that while most plants had round 

 stems, in some they were triangular, some quadrangular, 

 &c., but that, so far as he knew, no attempt had been made 

 to explain these differences. He thought they could, how- 

 ever, be accounted for on mechanical principles. In build- 

 ing, when the main object was to meet a strain in one 

 direction, the well known girder was the most economical 

 disposition of material. In a tree-stem it was necessary to 

 resist strain coming from all directions, and the woody 

 tissues acted as a circular series of girders. In herbs with 

 opposite leaves the strains were mainly in two directions, 

 and were met by two opposite girders, thus giving the 

 quadrangular stem. Taking our native flora he showed that 

 all herbs with quadrangular stems had opposite leaves, and 

 as a rule herbs with opposite leaves had quadrangular stems. 

 Sedges had triangular stems and grasses round stems, and 

 while sedges had the leaves in threes, those of grasses were 

 distichous. Pentagonal stems might be accounted for in a 

 similar way, and incidentally this threw light on the petals 

 of so many flowers. Thus plants had adopted, millions of 

 years ago, principles of construction which have gradually 

 been worked out by the skill and science of our architects 

 and engineers. — Observations on some undescribed or little 

 known species of Hemiptera Homoptera of the family 

 MembracidiE : G. Bowdler Buckton. Prof. Poulton has 

 explained the significance of the strange forms of some of 

 the Membracidae by their dependence on environment, and 

 the requirements of mimicry ; and the Rev. Canon Fowler 

 has also given information respecting the economics of 

 the species, and their maintenance during the struggle for 

 life. The present paper may be regarded as supplementary 

 to Canon Fowler's work on the Membracidfe in the 



NO. 1832, VOL. 71] 



" Biologia Centrali-Americana," and to Mr. Buckton's 

 monograph, in which latter work an attempt has been made 



to classify the family so far as at present known. The 

 specific descriptions are chiefly founded on specimens from 

 the museums of Madrid and Brussels. Most of the new 

 species are from Mexico and Central America, six from 

 Africa, and one each from India, Ceylon, Sumatra, and the 

 Philippines. Mr. Buckton then characterises twenty-four 

 new species, five of which are made the types of new genera, 

 and the paper concludes with general observations on the 

 habits, economy, and transformations of the Membracidae. 



Physical Society, November 25. — Dr. R. T. Glazebrook, 

 F.R.S., president, in the chair. — The measurement of small 

 differences of phase : Dr. \V. E. Sumpner. Hitherto, in 

 order to measure the differences of phase between alter- 

 nating-current quantities, it has been necessary to use some 

 method involving the simultaneous reading of three de- 

 flectional instruments, such as the wattmeter method, or 

 the three-voltmeter method either in its original or in some 

 modified form. These methods cannot be successfully 

 applied when the phase-differences to be determined are 

 small. The author describes new voltmeter methods which 

 may be used for the purpose, and gives the results of a 

 number of measurements on alternating-current plant. — 

 Dr. C. V. Drysdale exhibited and described apparatus for 

 the direct determination of the curvatures of small lenses, 

 such as the objectives of microscopes. Parallel light from 

 a distant source falls upon a plane unsilvered mirror in- 

 clined at an angle of 45°. Some of the light is reflected and 

 brought to a focus by an ordinary convex lens. The surface 

 to be tested is placed at this point, and the reflected rays 

 proceed as if they had come from a point on the surface. 

 They pass through the plate glass into a telescope focused 

 for parallel rays, and an observer sees an image of the 

 distant source. If the surface is convex and is brought 

 nearer to the lens, then, when it reaches such a position 

 that its centre of curvature is at the focus of the rays 

 emerging from the lens, the light will again retrace its 

 former path and a distinct image of the source will be seen 

 in the telescope. In order to obtain the two images the 

 surface has therefore been moved through a distance equal 

 to its radius of curvature. If the surface is concave it must 

 be moved away from the lens. Dr. Drysdale showed how 

 the method could be carried out by means of an auxiliary 

 piece fitted to an ordinary microscope. He also described 

 a method of testing the spherical and chromatic aberration 

 of microscopic objectives. Light from a distant point is 

 partially reflected by means of a piece of plate-glass down 

 the axis of the microscope. In passing out of the objective 

 it is brought to a focus upon a mirror, and retraces its path 

 along the axis of the instrument until it reaches the plate 

 glass. This it passes through, and by means of a telescope 

 an observer can view the distant source. The light having 

 passed twice through the lens to be investigated, the effects 

 of chromatic and spherical aberration are doubled, and at 

 the same time the effect of coma is eliminated. — Prof. S. P. 

 Thompson gave an exhibition of specimens of crystals 

 showing the phenomenon of luminous rings. He said it 

 was well known that when a source of light was viewed 

 through certain samples of calc-spar the field of vision con- 

 tained two luminous rings each of which passed through 

 the image of the luminous point. The subject had been 

 investigated by Dr. Johnstone Stoney, who had attributed 

 the phenomenon to a minute tubular structure in the crystal. 

 There were, however, certain crystals which when cut in 

 the ordinary way across the a.xis and used to view a distant 

 source of light exhibited a single luminous ring passing 

 through the image of the source. Looking down the axis 

 of the crystals no ring is visible, but on tilting it a ring 

 can be seen in the direction of the tilt which grows in 

 diameter as the tilt is increased. So far as he knew, no 

 explanation of these phenomena had been offered. At the 

 meeting a piece of calc-spar showing the two rings, and 

 pieces of beryl and tourmaline showing the single ring 

 were exhibited. 



Edinburgh. 



Royal Society, November 7.— I-ord M'Laren in the 

 chair. — In a paper on Prof. Seeliger's theory of temporary 

 stars. Dr. J. Halm gave some important extensions bear- 

 ing especially upon the characteristics of Nova Aurigas (1892) 

 and Nova Persei (1902). Seeliger's theory, broadly stated, 



