268 



jVA TURE 



[December 31, 1908 



dilliculty, at Ic-ast in the presence of viscosity ; but the 

 impossibihty of a gain of energy shows that the motions 

 hfre contcmj>lated cannot be reversed. 



In order to recur to the natural condition of things 

 where the shallow water is at rest, we have to superpose 

 the velocity u taken negatively upon the above motion. 

 The velocity of the bore is then », and that of the stream 

 above the bore u — n'. If I is relatively small, it is much 

 greater than «'. 



The reasoning just used is very similar to that applied 

 by Stokes (_Pliil. Mag., vol. xx.\iii., p. 3^9, 1848) and by 

 Riemann {Gotlingen Abh., vol. viii., i860) to sound waves 

 of expansion moving- in one dimension. The matter is dis- 

 cussed in "Theory of Sound," § 253, where it is shown 

 that the discontinuous solution, obtained from the prin- 

 ciples of conservation of mass and momentum, violates the 

 condition of energy. When this was pointed out to Stokes 

 by Kelvin, and later by myself (Stokes, " Malh. and Phys. 

 Papers," vol. ii., p. 55), lie abandoned his solution, which 

 is, however, maintained by a competent German authoritv 

 (private correspondence). It is clear, at least, that when 

 the motion is such as to involve a gain of energ-y, the solu- 

 tion cannot be admitted. The opposite case stands upon 

 a different footing, and we may, perhaps, imagine the 

 redundant mechanical energy to be got rid of soniehow at 

 the surface of discontinuity. Even "then we should have 

 to face the complication entailed by the development of 

 heat. In the present case of liquid^ the heat is of little 

 consequence, and since the motion is not entirely in one 

 dimension, we escape the necessity of dealing with a single 

 plane of discontinuity. 



November 12. — " Further Observations on Welwitschia." 

 By Dr. H. H. W. Pearson. Communicated by Prof. 

 A. C. Seward, F.R.S. 



The material whicli forms the subject of this investiga- 

 tion was collected at Wclwitsch and Haikamchab, in 

 Damaraland, in January and February, 1907. Macro- 

 spores and embryo-sacs are frequently present in the pith 

 region of the female cone-axis. This confirms the view, 

 already adopted by most authors, that the ovule of Wel- 

 witschia is cauline. Sporogenous cells have not been found 

 in a similar position in the male cone. 



The female cone and the male flower arc probably 

 derived by reduction and specialisation from an amphi'- 

 sporanglate strobilus of a type similar to that of 

 Bennettites. 



.At the end of the free nuclear division the embryo-sar 

 contains about 1024 nuclei which are equivalent in all 

 visible characters. Cleavage of the cvtoplasm occurs, 

 resulting in the scptation of the whole sac into compart- 

 ments. In respect of the morphological character of the 

 endosperm, Gnetum and Welwitschia are widelv separated 

 from Ephedra, in which the endosperm is a prothallus of 

 the normal gymnosperm type. It is suggested that the 

 endosperm of the primitive angiosperms was honiolotrous 

 with that of Welwitschia. 



It appear.s that (i) the Gnetum-Welwitschia alliance has 

 Its origin in the same stock as the angiosperms, but 

 separated from the angiosperm line before the carpel 

 became the pollen-receiver : ^2) Welwitschia is the most 

 specialised living rcprfsenl.iiivf of the race to which it 

 belongs. 



Zoological Society, December i=;.— Dr. Hen.y Wood«•a"^ 

 H.R.S., vice-president, in the chair.— Some notes on the 

 muscular and visceral anatomv of the batrachian genus 

 Hemisus, with notes on the Ivmph hearts of this and other 

 genera : F. E. Beddard.— New species of Lacerta from 

 Persia : G. A. Bouleng^er.— Some wart-hog skulls in the 

 British Museum ; Dr. Einar LonnberK.— Two Chinese 

 Serow skulls: R. Lydekker.— Warning coloration in the 

 musteline Carnivora : R. I. Pocock.— .A new river-crab 

 of the genus Gccarcinucus, from New Guinea : Dr. W. T. 

 ***['"»" — Mammals collected in the provinces of Shan-si 

 .-ind Slien-si, northern China, bv Mr. M. P. Anderson, for 

 the Duke of Bedford's zoological exploration of eastern 

 Asia : Oldfield Thomas. Thirty-three species were in- 

 cluded, represented by 335 specimens, presented, as before, 

 to the Nalion.-il .Museum bv the Duke of Bedford. 



N-O. 2044, VOL. 70] 



I.inntan Snc'ct-. DecemLer 17. — Dr. U. H. Sci-it, 

 F.R.S., president, in the chair. — The .\nomura of the 

 Sudanese Red Sea : \\". Riddell. — Forms of flowers in 

 Valeriana dioica : R. P. Gregory. In 1S77 Hermann 

 MuUer described four forms of ]'alci'iaua ih'oica, dis- 

 tinguished from one another by the size of the flower and 

 by the relative development of the male and female re- 

 productive organs. The phenomenon appears to be very 

 similar to that which was described by Darwin in 

 Rhamniis calhartiiiis. It has been found that the in- 

 dividuals of J'tdcriaiia dioica may be conveniently arranged 

 in four g-roups, which are distinguished as, respectively, 

 "female," "hermaphrodite," "long-styled male," and 

 " short-styled male " ; but while the central types of each 

 group are readily distinguishable, it must be distinctly 

 recognised that they are connected by a series of inter- 

 mediate forms, and that there is no discontinuity between 

 successive groups. The precise structure of the flowers of 

 each plant varies considerably, as regards the relative 

 development of the reproductive organs, with the age of 

 the flower examined; but in addition to this there is, in 

 some cases, a very wide range of variation in this respect, 

 quite independent of the age of the flower. — Etudes sur 

 les Cirrhipedos du Mus<l-e de Cambridge : Prof. Gruvel. — 

 The Rhynchota obtained on the Sealarl: Expedition : 

 W. L. Distant. The author stated that the collection 

 made by Mr. Gardiner in the Seychelles comprises forty 

 species, viz. twenty-eight species of Heteroptera anil 

 twelve of Homoptera. Walker was the first to write on 

 the Heteroptera of these islands, and in 1872 he described 

 three species collected by Dr. Perceval Wright, one of 

 which vi'as found by Mr. Gardiner. In 1893 Bergroth and 

 Reuter worked out the collections made by M. Ch. .Alhi;uid 

 and Pere Philibert so far as the Heteroptera was con- 

 cerned, and were able to enumerate thirty-seven species. 



Geological Society, December 16. — Prof. W. J. 

 Sollas, F.R.S., president, in the chair. — The igneous and 

 associated sedimentary rocks of the Tourmakeady district 

 (County Mayo) : C. I. Gardiner and Prof. Sidney II. 

 Reynolds, with a palajontological appendix by F. R. C. 

 Reed. The succession of the Ordovician rocks of the dis- 

 trict appears to be as follows: — ? Bala beds; Llandeilo 

 beds : (c) Shangort beds ; (fc) Tourmakeady beds ; (n) red 

 felsite or rhyolite ; Arenig beds — Mount Partry beds : 

 (d) variable tuffs, grits, and cherts; (c) coarse quartzose 

 and felspathic grits ; (b) grits, graplolitic black slates, and 

 radiolarlan clierts ; (a) coarse conglomerates. A series of 

 graptolites from the Mount Partry beds prove to be of 

 Upper Arenig age — .about the zone of Didymograptiis 

 hinindo. The puzzling beds of the district are those of 

 Llandeilo asje. .\lthough the limestones (Tourmakeady 

 beds) occur in the main as disrupted blocks in the Shangort 

 beds, the fossils indicate that there is little difference in 

 the age of these deposits ; probably, after the deposition of 

 the limestone, but during the prevalence of the same faunal 

 types as ihose of that deposit, the limestone was broken 

 up by volcanic explosions, and its fragments were deposited 

 as the peculiar limestone-breccias. The intrusive rocks are 

 in the main felsites with quartz-crystals, and often contain 

 augite. Interesting intrusions of olivine-dolerite, horn- 

 blende-lamprophyre, and fine-grained oligoclase-bearing 

 rocks arc scattered throughout the district. The nppendix 

 embodies a description of new s[K'cies of br:ich;op()(ls and 

 trilobitcs. 



P.ARIS. 



Academy of Sciences. Dereniber i (. — M. Bnurhnrd in ihe 

 chair. — The approximate calculation of inequalities of a 

 high order : .Maurice Hamy. A calculation to the .second 

 degree of approximation of the disturbance of one planet 

 by another. — Contribution to the study of Hacnwgrcgarina 

 lacertae of Danilewslvy and Chalachnikow : .A. Laveran 

 and .\. Pettit. .V detailed account of the appearances of 

 this parasite in various stages of development, with nine 

 illustrations. — Observations concerning the direct dehydra- 

 tion of certain alcohols : Louis Henry. In an earlier paper 

 it has been shown that dimethyl-isopropyl-carbinol, heated 

 with acetic anhydride and a few dirops of sulphuric .acid, 

 gives, not the acetate, but a mixture of the hydrocarbons 



