June i, 191 i] 



NATURE 



471 



>ent paper describes experiments, intended to test these 

 deductions. The results show that in the cases considered 

 the second deduction is verified, and the first also, when 

 the test can be pushed t;o completeness. In some cases 

 insufficient knowledge of the law of absorption of the 

 kathode rays, and of other important processes, prevent 

 the full application of the test, but it is satisfactory so 

 far as it goes. — Prof. A. Fowler and the Hon. R. J. 

 Strutt : Spectroscopic investigations in connection with 

 the active modification of nitrogen. I. — Spectrum of the 

 afterglow, (i) The paper gives a detailed account of the 

 spectrum of the afterglow of pure nitrogen, with wave- 

 length determinations of sufficient accuracy to indicate the 

 series relationships of the various bands. (2) The charac- 

 teristic bands of the afterglow in the red, yellow, and 

 green are complex groups which have been found to be 

 identical with some of the bands forming the sequence 

 known as the first positive group of nitrogen. They repre- 

 sent a special development of three of the numerous series 

 into which the first positive bands have been divided. 

 {3) The second group of afterglow bands, extending from 

 4312 to 2503, corresponds with a group of faint bands 

 which occur in the uncondensed discharge in air or 

 nitrogen, and the third group is identical with the third 

 positive group of nitrogen bands, as previously shown by 

 Lewis. (4) The most characteristic feature of the con- 

 densed discharge which produces the afterglow is a series 

 of seven complex bands, occupying the region 2904 to 2256, 

 which have not previously been recorded as belonging to 

 nitrogen. It is suggested that these should be designated 

 the '■ fourth positive " group of nitrogen bands. (5) No 

 afterglow is excited when the discharge is such as to give 

 only the line spectrum of nitrogen. — C. Cuthbertson and 

 Mrs. M. Cuthbertson : An optical method of measuring 

 vapour pressures : vapour pressure and apparent super- 

 heating of solid bromine. The vapour pressures of solid 

 bromine between —80° C. and the melting }>oint have been 

 measured by counting the number of interference bands 

 which pass across the field of a Jamin refractometer as 

 the temperature of the solid is gradually raised. The 

 vapour-pressure curve obtained agrees well with that 

 observed by Ramsay and Young down to — 17° C. The 

 behaviour of the vapour pressure near the melting point is 

 remarkable, and suggests the inference that superheating 

 of the solid occurs. — Dr. Frank Norton : The vacuum- 

 tube spectra of mercury. Under certain conditions, 

 mercury vapour may be made to give several different line 

 spectra in which the number of lines appearing ranges 

 from 5 in the simplest case (the yellows 5791, 5770, the 

 green 5461, the blue 4916, and the violet 4359) to a very 

 large number in the case of the " many-lined spectrum " 

 first observed by Eder and Valenta. The observations 

 were made directly by means of a direct wave-length 

 reading spectroscope, and several new bright lines are re- 

 corded in the red and orange regions of the spectrum. 

 The luminosity was excited in three different ways : — 

 (i) by means of the discharge from a glowing lime 

 kathode; (2) by an induction-coil discharge through the 

 vapour at different pressures, and with different amounts 

 of capacity in the circuit ; (3) by means of the electrodeless 

 ring discharge. Five distinct spectra were recognised, all 

 of which may be obtained with the induction-coil dis- 

 charge by suitably regulating the conditions. The glow- 

 ing lime discharge gives one of the simplest spectra ; the 

 electrodeless ring discharge gives the sjxictrum containing 

 most lines. — R. Whiddingrton : The production of 

 characteristic Rontgen radiations. A characteristic radia- 

 tion can usually only be excited when the velocity of the 

 kathode rays within the X-ray tube supplying the primary 

 rays exceeds a certain value, depending on the radiator. 

 The value of this critical speed, v„ has been accurately 

 determined for the radiators Cr, Fe, Ni, Cu, Zn, Se ; 

 that for Al has been given in a previous paper. It appears 

 that, for the radiators studied, v^ is proportional to the 

 atomic weight of the emitting element, being very nearly 

 10' times the atomic weight. The potentials corresponding 

 to these velocities range between 7320 volts and 15,400 

 volts. An interesting result obtained during the course of 

 the investigation is that the energy emitted in the form of 

 Rontgen radiation by a kathode particle whf^n suddenly 

 stopped is proportional to the fourth power of its velocity. 



NO. 2170, VOL. 86] 



Linnean Society, May 4.— Dr. D. H. Scott, F.R.S., 



president, in the chair, afterwards Prof. Poulton, F.R.S., 

 vice-president.— Rev. T. R. R. Stebbing: : John \'aughan 

 Ihompson and his polyzoa, and on Vaunthompsonia, a 

 genus of sympoda. In comparing the claims of polyzoa 

 and bryozoa to be the name of a class, the paper submits 

 the following propositions : — (i) A majority of writers use 

 bryozoa. (2) As used by Thompson, polyzoa is a word in 

 the singular number ; as used by Busk and his followers, 

 it is in the plural ; therefore, as Busk candidly points out, 

 the words are not synonymous. (3) For a class-name the 

 plural is essential, and thereby Ehrenberg's bryozoa 

 obtains priority. (4) Polyzoa in the singular was first used 

 by Lesson, who gave the name to a genus of compound 

 ascidians. (5) Thompson himself placed the genera and 

 species in which he had observed " Polyzoae " in the class 

 Mollusca acephala. (6) It was not Thompson, but Grant 

 (in his observations on Flustra.') who first drew the dis- 

 tinction between these p>olyps and the hydroid polyps with 

 which they had been confused. This again is pointed out 

 by Busk. (7) As Waters long ago, and again recently, 

 has insisted, Thompson meant by Polyzoa, not a class, 

 but a polypide, a structural element in certain organisms. 

 Possession of vertebrae distinguishes a codfish from a crab- 

 fish and a shellfish, but no one would think of proposing 

 Vertebra as a jilural word for the name of a class or 

 phylum. A supplementary notice vindicates Vaunthomp- 

 sonia as the correct form for Bate's sympodan genus in 

 opposition to Vauntompsonia of later introduction, and 

 gives reasons for discarding the term cumacea in favour 

 of sympoda. — Dr. F. F. Fritsch : Fresh-water alg;c 

 collected in the South Orkneys by Mr. R. N. Rudmose 

 Brown. Comparison was made between the algal floras 

 of the South Orkneys and South Georgia, and special 

 attention was directed to the constituents of the " Yellow 

 Snow." — Prof. Sydney J. Hickson : Polytrema and some 

 allied genera. The discovery of some very large speci- 

 mens of foraminifera belonging to the species described by 

 Carter as Polytrema cylindricum in the material collected 

 by Prof. Stanley Gardiner in the Indian Ocean led the 

 author to make a careful examination of this and of other 

 species attributed to the genus Polytrema. The result of 

 this examination was to prove that the specimens usually 

 labelled Polytrema in collections may belong to three quite 

 distinct genera. Polytrema cylindricum of Carter is the 

 type of a genus for which the generic name Sporadotrema 

 is proposed. The specimen described by Carpenter under 

 the name Polytrema rubra (Lamk.), and many other speci- 

 mens that are labelled Polytrema miniaceum (Pallas) in 

 collections belong to another genus, for which the generic 

 name Homotrema is proposed. The specimens described 

 by Merkel, Lister, and others under the name Polytrema 

 miniaceum belong to a genus distinct from the other two, 

 and for this it is proposed that the generic name Poly- 

 trema be retained. .A description of the principal 

 characters separating the three genera is given in the 

 paper. — J. M. Brown : Observations on some new and 

 little known British rhizopods. — R. Shelford : The 

 British Museum collection of Blattida? enclosed in amber. 



British Psychological Srciety, May 6. — Prof. Cirveth 

 Read : The psychology of genius. The chief condition of 

 genius is sensitiveness to analogy supported by extra- 

 ordinary power of registering experiences, perhaps without 

 consciously attending to them, in such a way that, 

 although they cannot normally be reproduced, they 

 influence by an.ilogy future constructive* or analytic |)ro- 

 cesses. — Miss E. M. Smith : Some ohserv.itions concern- 

 ing colour vision in dogs. — \V. H. Winch : Some new 

 exercises in reasoning suitable for the mental diagnosis of 

 school children. 



Zooloo'ical Societv. May o. — Mr. E. G. B. Meade-Waldo, 



vicc-prosident, in the chair. — Lieut. -Colonel Neville 

 Manders : The phenomena of mimicry amongst butter- 

 flies in Ikiurbon, Mauritius, and Ceylon. The author had 

 investigated the habits by observation and experiment of 

 the insectivorous reptiles and birds of these islands, and 

 had been unable to accept the view that their relations to 

 butterflies were such as to be effective in producing 

 Batesian or Miillerian mimicry. — R. I. Pocock, F.R.S. : 

 The palatability of some British insects, with notes on 



