February 2^^, 1922] 



NATURE 



253 



I sh 



I 



I Sim 



pear- or kidney-shaped or more or less irregular, rod- 

 shaped, and branched. They are readily stainable, 

 enerally motile, and fairly resistant. They may 

 ultiply by fission or budding, are formed from 

 egetative cells or from the symplasm, and may give 

 ise to vegetative cells or to the symplastic stage. 

 ) Exospores, unstainable regenerative bodies. (4) 

 ndospores, produced by vegetative cells or by re- 

 generative bodies. Conditions for formation are 

 similar to those for the formation of regenerative 

 ies. (5) Arthrospores, easily stainable, but with- 

 and drying better than heating. They are formed 

 by the segmentation of vegetative cells and trans- 

 formation of the joints into fairly resistant spherical 

 bodies. (6) Microcysts, very simuar to arthrospores. 

 hey are formed by vegetative cells growing and 

 coming spherical with a thickened membrane, 

 fter a rest period they may become vegetative cells, 

 rminate like spores, or may break up into two, 

 ree, or four segments, which become vegetative 

 lis. In addition to their reproductive function exo- 

 res, endospores, arthrospores, and microcysts are, 

 the first place, resting-stages. 



Besides the formation of the symplasm a second 

 mode of interaction between the protoplasmic bodies 

 in bacterial cells has been observed. This consists 

 in, the union of two or more cells, and is termed 

 "conjunction" by the author. Conjunction is most 

 common in cultures two to four days old, and 

 generally precedes the formation of gonidia, repro- 

 ductive bodies, exospores, and endospores. 



The publication brings together an overwhelming 

 amount of evidence as to the existence of the various 

 forms distinguished by the author. The arrange- 

 ment of these forms in the life -cycles of the bacteria 

 is a point on which further information is desirable, 

 but this will, doubtless, be provided in the later pub- 

 lication in which the observations of the author are 

 to be dealt with in detail. From the point of view 

 of the student of bacterial morphology the publica- 

 tion must be regarded as one of first-rate importance. 

 The general worker on bacteriological problems will 

 also find in it much information of a highly valuable 

 nature, and doubtless will be able to confirm the 

 existence of many of the forms observed from the 

 results of his own experience. 



Miners' Lamps.' 



F late years there has been a tendency on the 

 part of makers of miners* safety lamps to em- 

 !oy thin sheet-metal, perforated with holes of small 

 meter, to serve the same purpose as wire gauze — 

 at is to say, with holes large enough to admit of 

 e passage of the necessary volume of air through 

 em, but small enough to arrest the passage of 

 me. It will be recalled that the lamp invented by 

 orge Stephenson depended upon perforated sheet- 

 pper for its impermeability to flame, A further 

 novation that has recently been gaining ground is 

 e addition of a short glass cylinder, known as the 

 combustion tube," to the lower end of a metal 

 imney suspended directly above the flame of the 

 lamp. This contrivance promotes a better circulation 

 of air in the lamp, keeps the products of combus- 

 tion separate from the incoming air, and, as a con- 

 sequence, produces a brighter flame and enhances the 

 lighting power of the lamp. 



Metal chimneys have long been employed with this 

 obiect, notably in the Mueseler lamp — the only kind of 

 safety lamp permitted in Belgian mines— but as the 

 bottom of the metal chimney cannot be brought lower 

 down than the top of the flame without obstructing 



1 Mine<: Department. Miners' Lamps Committee. Memorandum No. 4 : 

 Record of research on the passage of flame through perforat'd pbtes and 

 through perforated tuhes of small d-'ameter. Pp. 12+6 plates. (H.M.S.O.) 

 q«. net. Memorandum No. 5 : Record of research on the passage of the 

 flame of an explosion from within miners' lamps fitted with chimnevs. 

 Pp. 12. (H.M.S.O.) 6rt'. net. 



the light, the benefit derived frotn their use is limited. 

 In this respect the glass extension is distinctly 

 beneficial. 



Having regard to the changes of this kind which 

 were taking place in the construction of safety lamps, 

 the Home Secretary appointed the Miners' Lamps 

 Committee in 19 19 to inquire into, and rep>ort on, 

 various questions relating to safety lamps, and the 

 Secretary for Mines re-appointed the same Committee 

 in January, 192 1. Up to the present the Committee 

 has issued five Memoranda, of which the last two, 

 Nos. 4 and 5, issued in the end of last year, deal 

 with the use of perforated metal plates and chimneys 

 respectively. 



The experiments described in Memorandum No. 4 

 were made to ascertain the relative resistance to the 

 passage of flame possessed by metal plates of various 

 thicknesses perforated with holes of various diameters ; 

 and those described in Memorandum No. 5 to ascer- 

 tain the relative resistance of chimneys of various 

 lengths and diameters at top and bottom and extend- 

 ing to higher or lower levels above and below the wire 

 gauze diaphragm by which they are supported. 



The results are tabulated in both memoranda and 

 in the letter to the Secretary for Mines which accom- 

 panies each the chairman of the Committee makes 

 certain recommendations and suggestions founded 

 on these results. The total cost of the Committee's 

 inquiry to date (November, 192 1) is given as 5550?. 



P^brine in Silkworms. 



TN an interesting report on pebrine in silkworms in 

 India (Memoirs Dept. Agric. in India, Bacterio- 

 logical Series, vol. i, No. 8, November, 1920, pp. 75, 

 26 plates), Mr. C. M. Hutchinson gives an account of 

 experimental work on methods of infection. He 

 found infected ova in the pupal ovarv, and the infec- 

 tion is traced in the egg, larva, and pupa— and re- 

 counts the life-history of the causal organism, Nosema 

 bnmbycis. The Pasteur method of searching for the 

 organism, devised more than fifty years ago, con- 

 sists in crushing the body of the moth in a mertar, 

 and examining, under a magnification of about 600, 

 a small fraction of the resulting powder in a drop 

 NO. 2730, VOL. 109] 



of water, to ascertain if the characteristic spores 

 of Nosema are present. This method, according to 

 the author, has not been attended in India with any 

 approach to the measure of success which has been 

 attained in Europe. The chances of non-detection of 

 infected moths, and the risk of spreading the spores 

 (due to careless application of the method) in the 

 rooms used for examining the moths, are consider- 

 able— ^the author states that he has seldom failed to 

 find Nosema spores in the floor dust from these rooms, 

 even in cases where the floors were of concrete. In 

 Europe a period of several months elapses between 

 oviposition by the moth and hatching of the eggs, so 



