296 



SCIENCE-GOSSIP. 



A Myxomycetous Parasite. — M. E. Roze has 

 detected Psetido-commis vitis, a myxomycete, in the 

 hypodermal cells of the tubers, as well as in the 

 eaves, of diseased potatoes. It occurs in the form 

 of plasmodes and of cysts, and attacks both the 

 cell-nucleus and the starch grains. According to 

 the author, it occurs very commonly in garden 

 and greenhouse plants. The black and brown 

 spots, which indicate the malady known to 

 gardeners as " burning," are due to the attacks of 

 this parasite. It is often overlooked owing to its 

 very rudimentary structure, consisting of a plas- 

 mode-like mucus, which becomes encysted in 

 certain conditions. As long as the plasmode is 

 in a living condition it is able to escape, under 

 favourable conditions, and infect other vegetable 

 tissues. 



The Sporular Development of Amoeba 

 villosa. — Mr. J. C. Smith gives an interesting 

 account in the " American Microscopical Journal " 

 of his observations on the sporular development 

 of Amoeba villosa. He obtained his specimens by 

 scraping the surfaces of some decayed leaves from 

 a park pond ; and he conducted his observations 

 with a J-inch objective. One of the specimens was 

 seen to contain a number of nuclear bodies that 

 varied in size from a ,J 50 - to y^j-inch, which, after 

 a short time, were ejected from the Amoeba with 

 considerable force. The nuclear bodies shortly 

 afterwards developed flagelli equalling in length 

 from four to five of the bodies' diameters, and 

 became exceedingly active. From this point the 

 writer describes in some detail the full life-history 

 of these bodies, in the course of which he shows 

 how the A. villosa are once more evolved. To 

 make this history of the sporular development 

 of the A. villosa (and by inference all Amoeba) 

 complete there is only one essential requisite, and 

 that is to trace the origin of the nuclear-looking 

 bodies to the nucleus. 



Microscopic Sections of Oolitic Grains. — 

 In reply to T. W. P. (Brighton), we would recom- 

 mend the following method for sectioning any 

 fragmental substances as being, in our experience, 

 both simple and effective. Further details may be 

 obtained from Dr. Wallich's article in " The 

 Annals and Magazine of Natural History," vol. 

 viii. p. 58 ; from Professor Cole's " Aids to 

 Practical Geology " ; or from an article by Mr. 

 F. Chapman which appeared in " Scientific News," 

 vol. i., p. 452. A small glass slip or square cut 

 from plate glass is laid upon a metal plate over a 

 spirit-lamp. A drop of nearly dried balsam is 

 softened upon this by heat, and a plate of mica is 

 laid on it, becoming thus cemented to the glass. 

 The small objects, of which sections are to be 

 prepared, are then embedded in further balsam 

 upon the mica surface and arranged in any suitable 

 position. When this balsam is cold and firm the 

 glass is used as a handle, by which the objects can 

 be held during grinding. A flat surface is then 

 given to them as they lie in the balsam by rubbing 

 on a hone. Lightly heat the glass, and as soon as 

 the lower film of balsam between the mica and the 

 glass softens, lift up the mica with a pair of 

 forceps and turn it over on to an ordinary glass 

 slip on which a little balsam has been heating. 

 The ground surface of the objects is now down- 

 wards, and when cold the mica may be flaked 

 off the upper surface. Using the new slip as a 

 handle, the newly exposed side may be ground 

 down to the required degree of thinness. 



NEW TYPE OF MICROSCOPE. 



T N consequence of the rapidly increasing necessity 

 for microscopes of an inexpensive character, 

 Messrs. Ross, Limited, of in, New Bond Street, 

 London, have produced a remarkably useful as 

 well as cheap instrument, of which we give an 

 illustration. 



In designing this special type of microscope, the 

 firm has had in view its increased use in connection 

 with research in agricultural and horticultural, as 

 well as other sciences. It is intended to be further 

 applied to the textile trades, and examination of 

 produce and raw materials. The pattern of this 

 instrument has been arranged in view of the fact 

 that many of its future users require the simplest 

 form ; and one free from unnecessary compli- 

 cations. At the same time stability and steadiness 

 are absolutely necessary for its successful use. 

 This has been achieved. Remembering that the 

 class who are likely to purchase such an instru- 

 ment as this will require it for use in their pro- 

 fessional or trade occupations, Messrs. Ross have 

 provided one which can be sold at so low a price 

 as three guineas, including limb, choice of ij-inch, 



i-inch or i-inch objective, eye-piece, mirror, rack 

 adjustment, sub-stage plate.and glass dish for liquids. 

 If the purchaser finds that he requires additional 

 parts, these can be obtained either at once or later, as 

 required. They include objectives, fine adjustment, 

 iris diaphragm, fitting stage, condensing lens fitting 

 stage, double nose-piece, etc. A fitting beneath the 

 stage of the instrument in its simplest form carries 

 a plate with diaphragm apertures. These are to 

 modify the light, and as opaque objects, such as 

 seeds and fibres, will form a large proportion of 

 those to be examined, this sub-stage plate has 

 a space between the perforations which, when 

 brought into position, provides a dark ground by 

 preventing the passage of light from underneath. 

 This fitting is removable, to allow the use of an 

 iris diaphragm if desired. 



Altogether, this instrument, which is named the 

 " Industrial Microscope," is produced with that 

 excellence for which Messrs. Ross, Limited, are 

 well known, J T. C. 



