52 



NA rURE 



[November 12, 1908 



Other observalions on Lomcchusa seem to show that the 

 numbers of ant-guests are kept down to a moderate level, 

 and if they become too numerous, they are killed off to re- 

 duce their numbers sufficiently to suit the ants, the 

 survivors being protected. Indeed, some of the beetle- 

 guests of the ants may live to the age of two or three years 

 in the nests. 



Other observations relate to mixed nests of Formica 

 cxsecta and fiisca, which are met with in a state of nature. 

 The development of such colonies, and their generallv 

 hostile treatment of Atemeles and other beetles, is dis- 

 cussed in detail. 



Further observations relate to experiments on the rear- 

 ing of other species of worker-pupa; in the nests of Formica 

 truncicola, with similar experiments, for comparison, 

 with other ants. While worker-pupje of F. fiisca are 

 adopted and reared by F. truncicola, those of other species 

 of ants are mostly destroyed, sooner or later, if they are 

 introduced into their nests. It was noticed that some 

 months after the reception of F. fusca into one of the 

 nests the queen of F. truncicola had become perceptibly 

 darker, but whether this was due to the presence of the 

 darker species (F. fusca) or was merely the result of old 

 age requires further investigation. Interesting observations 

 are also recorded respecting the migration of ant colonies, 

 and on their behaviour after the death of the queen. 



.■\nother section of the papers is devoted to experiments 

 on the founding of colonies, with special reference to the 

 parasitic and slavc-holdhig species of Formica. Sometimes 

 queens of one species are adopted into the nests of other 

 species, but sometimes they are attacked and killed. 



Further observations relate to the founding of colonies 

 of Polyergus, .Strongylognathus, and Anergates. Of these, 

 the latter is the most interesting genus. These curious 

 ants develop only into males and females, without workers, 

 and live parasitically in the nests of ants of the genus 

 Tetramorium, where their colonies are met with only 

 rarely, but where they are found they are very numerous. 

 The males are small and wingless. .So much was previously 

 known, and Father Wasmann's latest experiments do not 

 throw much fresh light on the subject. 



Finally, the author discusses the relationship between 

 parasitism and slavery in ants (which he regards as closely 

 connected), with special reference to Wheeler's views on 

 the subject. These phenomena cannot be explained on 

 phylogenetic principles, on account of the wide differences 

 between the species, which often dwell together in mi.xed 

 colonies. We have not sufficient space to follow this ques- 

 tion further, but strongly recommend 

 students who are interested in ants to wade 

 through Father \\'asmann's papers for 

 themselves, for though the observations are 

 sometimes tedious, and seem to us to 

 include a good deal of superfluous detail, 

 yet they include a great amount of material 

 which must be taken into account bv all 

 who interest themselves in the numerous 

 problems presented by the habits and 

 psychology of ants. W. F. Kirby. 



that a magnetic force which would deflect kathode rays 

 to a very considerable e.xtent was quite without effect on 

 the " Kanalstrahlen." By using intense magnetic fields, 

 W. Wien showed that these rays could be deflected, and 

 that the deflection was in the opposite direction to that 

 of the kathode rays, indicating; that these rays carry a 

 positive charge of electricity. This was confirmed by 

 measuring the electrical charge received by a vessel into 

 which the rays passed through a small hole, and also by 

 observing the direction in which they are deflected by an 

 electric force. By measuring the deflections under mag- 

 netic and electric forces, Wien found by the usual methods 

 the value of e/m and the velocity of the rays. He found 

 for the maximum value of ejm the value 

 of 10', which is the same as that for an ^ 



atom of hydrogen in the electrolysis of - 



solutions. A valuable summary of the 

 properties of these rays is contained in a 

 paper by Ewers (" Jahrbuch der Radio- 

 aktivitat," iii., p. 291, 1906). 



As these rays seem the most promising 

 subjects for investigating the nature of 

 positive electricity, I have made a series 

 of determinations of the values of e/m for 

 positive rays under different conditions. 

 The results of these I will now proceed to 

 describe. 



Apparatus. 



i-i^0^ 



Screen used to Detect the Rays. — The 

 rays were detected and their position deter- 

 mined by the phosphorescence they pro- 

 duced on a screen at the end of the dis- ^ 

 charge-tube. .A considerable number of 

 substances were examined to find the one F"" ■• 

 which would fluoresce most brightly under 

 the action of the ravs. As the result of these trials wille- 

 mite was selected, this was ground to a very fine powder 

 and dusted uniformly over a flat plate of glass. Consider- 

 able trouble was found in obtaining a suitable substance to 

 make the powder adhere to the glass. All gums, &c., 

 when bombarded by the rays are liable to give off gas; 

 this renders them useless for work in vacuum-tubes. 1 he 

 method finallv adopted was to smear a thin layer o 

 " water-glass " (sodium silicate) over the glass plate, .and 

 then dust the powdered willemite over this layer and al ow 

 the water-glass to dry slowly before fastening the plate 

 to the end of the tube. 



RAY.S OF POSITIVE 

 ELECTRICITY.' 

 TN 1886 Goldstein discovered that when 

 ■'■ the kathode in a discharge-tube is 

 perforated, rays pass through the openings 

 and produce luminosity in the gas behind 

 the kathode ; the colour of the light de- 

 pends on the gas with which the tube is 

 filled, and coincides with the colour of the 

 velvety glow which occurs immediately in 

 front of the kathode. The appearance of 

 these rays is indicated in Fig. i, the anode 

 being to the left of the kathode KK. 

 Since the rays appeared through narrow channels in the 

 kathode, Goldstein called them " Kanalstrahlen "; now that 

 we know more about their nature, " positive rays " would. 

 1 think, be a more appropriate name. Goldstein showed 



The form of tube adopted is shown in Fig. 2. A hole 

 is bored through the kathode, and this hole leads to a very 

 fine tube F. The bore of this tube is made as fine as 

 possible, so as to get a small, well-defined fluorescent patch 

 on the screen. These tubes were either carefully made 

 glass tubes or else the hollow thin needles used for hypo- 



NO. 20.^,7, VOL. 



79] 



