July 12, 1906] 



NA TURE 



261 



ment of the testis, before the tubules or pockets are 

 formed, it is impossible lo discriminate between the cells 

 destined to become foot-cells and the leucocytes or their 

 immeiiiate ancestors in the same animal. 



Amuiig these cells, also, divisions are seen where the 

 chromosome number is half what is found in the somatic 

 cells. The conclusion drawn from this is that the un- 

 differentiated cells which surround ihe male ova, and 

 which eventually form both the foot-cells and the walls of 

 the pockets or tubules of the testis, are derived from leuco- 

 cytes or have immediately common ancestors. If these 

 observations be correct, we have, therefore, animal cells 

 which, though reduced, form tissues possessing somatic 

 characters and functions known to happen in plants. 



The bearing of these observations upon the cancer 

 problem is obvious when the fusion between leucocytes and 

 tissue cells recorded elsewhere is borne in mind. 



May 17. — •' Some Physical Constants of Ammonia : a 

 Study of the Effect of Change of Temperature and Pressure 

 on an Easily Condensible Gas." By Dr. E. P. Perman 

 and J. H. Davies. Communicated by Principal E. H. 

 Griffiths, F.R.S. 



(i) The vapour density of ammonia at o° has been found 

 to be 0.77085 (inass of i litre in grams at latitude 45°), 

 previous results being 07708 by Guye and 0-7719 by 

 Le Due. 



(2) When the ammonia and the glass vessel were 

 thoroughly dried no appreciable adsorption of ammonia by 

 glass, or condensation of ammonia on the surface of glass, 

 was found to take place. 



(3) From density determinations at different temperatures, 

 the coefficient of e.xpansion of ammonia has been deduced 

 as 0003914 between 0° and —20°, and 0003847 between 

 0° and 100°. 



(4) From Rayleigh's determination of the compressibility 

 of ammonia and our own value for the density, the mole- 

 cular weight of ammonia has been calculated as 17030, 

 and the atomic weight of nitrogen as 14007. 



(5) Incidentally, the density of air free from water 

 vapour and carbon dioxide has been determined as 1-2920 

 (lal. 45°). 



(6) The deviation from Dalton's law for a inixture of 

 approximately equal volumes of air and ammonia has been 

 found to be about i part in 1000. 



(7) The pressure-coefficient of ammonia has been deter- 

 mined, the pressure being atmospheric at 15°. Between 

 0° and —20° the coefficient was 0-004003, and between 0° 

 and 98° it was o 003802. 



The determination of the vapour . pressure of liquid 

 ammonia was repeated at some of the lower teinperatures, 

 using pure ammonia, in order to obtain an accurate value 

 for its boiling point. From the results, the boiling point 

 of liquid ammonia at 760 mm. pressure was found to be 

 -.13°-S C. 



June 7. — " On the Osmotic Pressures of some Concen- 

 trated Aqueous Solutions." By the Earl of Berkeley and 

 E. G. J. Hartley. Communicated bv W. C. D. Whetham, 

 F.R.S. 



This communication gives an account of measurements 

 of osmotic pressures of aqueous solutions of cane sugar, 

 dextrose, galactose, and mannite. The method adopted is 

 that briefly outlined by us in vol. Ixxiii., Roy. Soc. Proc. 

 A gradually increasing pressure is placed upon the solu- 

 tion (which is separated from the solvent by a semi- 

 permeable membrane) until the solvent, which at first 

 flows into the solution, reverses its direction, and is 

 squeezed out. The pressure, when there is no movement 

 of the solvent, is considered to be the osmotic pressure. 

 Owing to the difficulty of determining the exact point at 

 which no movement takes place, and for other reasons, 

 the experiments are carried out so as to enable an observ- 

 ation to be made of the rate of movement of the solvent, 

 both when the pressure on the solution is just below and 

 when just above the turning-point pressure. The osmotic 

 pressure is deduced from these rates. The range of 

 pressures covered by the experiments is from 12 to 135 

 atmospheres. 



A description is also given of the methods adopted for 



NO. T915, VOL. 74] 



making the copper ferrocyanide membranes, and it is 

 pointed out that with the best membranes, in most cases, 

 a small quantity of solution comes through during the 

 experiment. It is shown that even a small leak causes 

 a considerable lowering of the observed pressure, hence 

 the final results accepted are those where the leak was 

 least. 



Attention is directed to the fact that the osmotic pressures 

 of cane-sugar solutions, when measured directly and when 

 calculated from their vapour pressures, agree lo within 

 3 per cent. 



Zoological Society, June 19. — Sir Edmund G. Loder, 

 Bart., vice-president, in the chair. — The nudibranchs of 

 southern India and Ceylon, with special reference to the 

 collections and drawings preserved in the Hancock Museum 

 at Newcastle-on-Tyne : Sir Charles Eliot. This paper was 

 an attempt to settle the synonymy of various Nudi- 

 branchiata of the Indo-Pacific with the help of Kelaart's 

 drawings and the collections made by him and Walter 

 Elliot, and now preserved at Newcastle. It also contained 

 some new information as to the anatomy of several species 

 (particularly Platydoris formosa, P. papillata, Doriopsilla 

 miniata, Kalinga ornata, and several Pleurophyllidiidte). 

 — An account of the Entomostraca taken during a bathy- 

 metrical survey of the .New Zealand lakes, and a com- 

 parison of this fauna with that of the English lakes : Dr. 

 G. S. Brady. — A paper dealing with the higher Crustacea 

 obtained during the above-mentioned survey : Prof. C. 

 Chilton. — A classification of the Selachian fishes : C. T. 

 Regan. The author stated that the Selachii were regarded 

 as entitled to rank, at least, as a well-marked subclass, 

 and he divided them into two principal groups, viz. 

 Trematopnea and Chasmatopnea, the latter including the 

 single order Holocephali. — An account of the polyclad 

 Turbellaria from the Cape Verde Islands collected by Mr. 

 C. Crossland : F. F. Laidlaw. The collection shows that, 

 on the whole, the fauna of this region of the Atlantic 

 agrees closely with that of the Mediterranean so far as 

 the polyclads are concerned. The most interesting of the 

 sixteen or seventeen species represented in the collection 

 are, perhaps, a species of .Anonymus (of which several 

 specimens were taken'l and Traunfelsia elongata, gen. 

 et sp. nov. The latter is an elongated form remarkable 

 for the possession of marginal tentacles, which are not 

 usuallv associated with a long, narrow body in this class. 

 A unique feature in this genus is the presence of a pair 

 of alveolar glands, each with a long duct opening on 

 either side of antrum masculinum. The genus is referred 

 to the Diposthiid<-e of Woodworth. — A large unknown 

 marine animal observed off the coast of Brazil during a 

 cruise in the Earl of Crawford's yacht the Valhalla : 

 E. G. B. Meade-Waldo and M. J. Ni'coll (see p. 202). 



I Royal Microscopical Society, June 20. — Dr. Pukinfield 

 I H. Scott, F.R.S., president, in the chair. — The structure 

 i of some Carboniferous ferns : Dr. D. H. Scott. The 

 1 author pointed out the change which had taken place 

 during the last three years in our conception of the Carbon- 

 i iferous ferns. So many examples of fern-like plants were 

 now known to have borne seeds, or were suspected of 

 having been seed bearers, that comparatively few undoubted 

 ferns were left, and it was questioned whether, at least in 

 the Lower Carboniferous, true ferns existed. One family, 

 the Botryopterideae, was admitted to be well represented in 

 Lower as well as Upper Carboniferous times, and Mr. 

 Newell Arbor had proposed to establish a group of Primo- 

 filices to include this and other primitive ferns of the 

 Palaeozoic age. The object of the communication was to 

 give a few illustrations of this ancient race of ferns. The 

 Botryopterideae were first described, beginning with the 

 type-genus Botryopteris. The genus Zygopteris was next 

 considered. A new genus from the Lower Coal-measures 

 of Lancashire, for which the naine of Botrychioxylon was 

 proposed, was then described. Two or three other examples 

 of the family having been noticed, Dr. Scott described 

 certain annulate fern sporangia. The germination of spores 

 within a sporangium was demonstrated, and this spor- 

 angium had quite recently been identified as belonging to 

 Stauropteris Oldhamia. 



