December, igo6 



KNOWLEDGE & SCIENTIFIC NEWS. 



621 



laya " was read in the absence of the author, and was 

 illustrated by large-scale drawings and mounted speci- 

 mens. Mr. J. M. Coon read a paper on Connuvia 

 sepula, illustrated by lantern slides and mounted speci- 

 mens. Mr. A. E. Conrady gave a summary of his 

 paper on an early criticism of the Abbe theory made by 

 Dr. Altmann in 1880. Dr. Altmann endeavoured to 

 extend the Hclmholtz theory by maintaining that the 

 image should be considered as built up of diffusion 

 discs such as Helmholtz had dealt with in his paper of 

 1873. This paper brought a vigorous reply from Prof. 

 Abbe, in which he added very considerably to the previ- 

 ously published account of his theory, and he laid stress 

 on the difference between a self-luminous object and one 

 illuminated artificiallv. 



Quekett Microscopical Club. 



October ig. — Mr. C. F. Rousselet, F.R.M.S., gave 

 a corrected description and exhibited a specimen of the 

 rare rotifer Teiramasiix opoliensis. Mr. Jas. Burton 

 read a paper, " On the Reproduction of Mosses and 

 Ferns." The position in the vegetable kingdom of 

 these two groups and of their near allies was pointed 

 out. The various methods of reproduction met with 

 among plants were described, and attention was 

 directed to the fact that in the mosses and ferns both 

 the non-sexual and sexual methods were developed to 

 the utmost extent in one life-cycle, which cycle is 

 spoken of as a whole as " \n Alternation of Genera- 

 tions." Details of the methods of reproduction ob- 

 taining in the two groups under notice were given at 

 length, and the differences pointed out. The capsule 

 of the moss was shown to be the counterpart of the 

 fern-plant, while the prothallus corresponded with the 

 evident leafy stem of the moss. The structure of the 

 various organs, etc., involved was described. In these 

 two groups the two methods of reproduction are 

 balanced, neither is developed at the expense of the 

 other, and the ferns and mosses were cited as guides to 

 the processes that occur in the other divisions of 

 organic nature. 



Cytology of Bacteria. 



The Journal of the R()\al Microscopical .Society gives 

 a summ:;ry of some investigations by \. Guilliermond, 

 into the structure of Bacillus radicosus, which is well 

 suited for the purpose by reason of its large size, and 

 which have been recently published in Cpnipies Rendiis. 

 In a less than ten-hours-3ld culture, after fixation in 

 Zenker's fluid, and staining with iron-haematoxylin, 

 almost every cell shows a large, deeply-stained central 

 granule, which represents the first appearance of the 

 site of transverse fission, and is formed by the union 

 of two small lateral granules apparently derived from a 

 concentration of the cytoplasm; this large granule, or 

 bi-concavc disc, divides intO' two coloured bands, 

 through which the division of the two cells is effected. 

 .\fter 10 to 12 hours the cytoplasm becomes vacuolated 

 and filled with fine stained granules of varving size, and 

 later shows an alveolar structure filled with fine 

 granules resembling granules of chromatin. Tlie spore 

 appears at one of the poles as a small, deeply-stained 

 granule; it enlarges, takes an oval form, and becomes 

 surrounded by a thick membrane which prevents the 

 penetration of stains. The spore appears to be de- 

 rl\ecl in p.irt from a condensation of the granules of the 

 cytoplasm. 



The author concludes that a true nucleus does not 

 exist in a bacterium, and that such as have been 

 described by various authors are misrepresentations. 



but agrees with Schaudinn that bacteria contain a 

 chromatin more or less mixed with the cytoplasm, dif- 

 ferentiated at times and constituting the greater part 



of the spore. 



Demonstrating Life History- 

 Leucocytes. 



of 



A recent issue of the Royal .Society's Proceedings con- 

 tains a method devised by C. VI. Walker, for demon- 

 strating the life-history of leucocytes. He fixes the 

 material with Flemming's fluid (strong formula), 

 Hermann's fluid, acetic acid and absolute alcohol, cor- 

 rosive sublimate and acetic acid, and strong formic 

 acid. The author remarks that great care must be 

 taken with the processes of fixation, dehydration, im- 

 bedding, staining, etc. Extremely small pieces of 

 tissue should be placed in the fixative within about a 

 m.inute of the death of the animal or removal from the 

 Ijiving body. Dehydration should be carried out in 

 short stages, an increa.se of 10 per cent, of alcohol 

 being perhaps best. This does not apply to tissues 

 fixed in acetic acid and alcohol, or strong formic acid 

 (40 per cent.), from which the tissues are transferred 

 immediately to absolute alcohol. At the same time, it 

 is necessary that the tissues should not be left in alcohol 

 (under 80 per cent.) for more than two or three hours 

 after fixation. In imbedding, no higher temperature 

 than 45° C. should be used. Throughout the processes 

 of staining and mounting, the greatest care must be 

 taken that the sections do not become even partially 

 dried upon the slides. The author states that it is 

 necessary to use a lo-inch tube microscope, with 

 monochromatic light and apochromatic objective and 

 eye-piece, in order to obtain the best definition with 

 immersion lenses, and 27 or even 40 compensation 

 oculars, but he adds that anything approaching this 

 is impossible with the ordinary short-tube — a some- 

 what incomprehensible statement. 



Microscopical Slides. 



Messrs. Clarke and Page, of Leadenhall Street, have 

 sent me their new list of microscopical slides, micro- 

 scopes, objectives, and accessories. I have before 

 called attention to these slides, which are similar to 

 tho.se mounted and sold by Mr. Hornell, and many of 

 them are of great beauty, and moderate in price- 

 .\mongst the slides are some prepared and mounted 

 without pressure, including slides illustrative of marine 

 zoology, such as Bugiila lurbinaia, and .\nnelidae, 

 mounted fully expanded, triple-stained palates of 

 molluscs, mounted for polariscope, and a particularly 

 fine .slide of the head of a blow-fly, also mounted with- 

 out pressure, and showing the structure of the proboscis 

 in a way very different to its ordinary appearance when 

 mounted. 



Studies in Micropetrography. 



Mr. E. Howard .\dye is issuing a series of studies 

 in micropetrography, dealing with some 48 different 

 specimens, somewhat on the lines of his recent '' .\tlas," 

 each section Ixjing fully described, with bibliographical 

 references, and with a large coloured illustrative plate, 

 with key. In addition, actual chips of the rocks de- 

 scribed can be obtained for comparison and examination. 

 Further particulars can be obtained from the publisher, 

 .Mr. RolK'rt Sutton. 4^^, The Exchange, Southwark. S.E. 



[Communiccitions and enquiries on Hficroseo/'ieal malters should be 

 addressed to F. Sliillington Seales, "Jersey," St. Baniab.is Road, 

 Cambridge. Correspondents are requested not to send sfeeimens to be 

 named.] 



