2 3 8 



SCIENCE-GOSSIP. 



replace the solution with distilled water, and boil 

 for two or three minutes ; repeat the treatment 

 with boiled water three times, wash with a one per 

 cent, solution of acetic acid, and finally with cold 

 distilled water. The sections are then quite ready 

 for staining. 



Test for Tolu Balsam. — Failures in mounting 

 are often traceable to impurities in the re-agents 

 and materials used. The following test for purity 

 of tolu balsam, as recommended by Gehe, may not 

 be without value to those of our readers who may 

 have occasion to use this mountant. Mix a few 

 grammes of balsam with carbon-disulphide, draw 

 off a few drops of the solution, evaporate, and 

 cover the residue with sulphuric acid. Pure 

 balsam gives an intensely blood-red colour re- 

 action, while mixed colours are indicative of 

 adulteration with resin. 



Action of Light on Yeasts. — W. Lohmann, 

 who has recently being giving attention to this 

 subject, finds that exposure to the electric light of 

 more than eleven thousand candle power exerts a 

 decidedly retarding action on the multiplication of 

 the cells of Saccharomyces cerevisiae. Observations 

 in the action of sunlight showed that the sun's 

 rays are even more disastrous in their effects, for 

 after several hours' direct exposure during May 

 and June the cells were entirely destroyed. A 

 moderate amount of light produces no such effect, 

 multiplication taking place as vigorously in that case 

 as in the dark. According to " Nature " a micros- 

 copic examination revealed a striking morphological 

 difference between cells kept in the dark and 

 others which had been isolated. The former 

 preserved a perfectly normal appearance, but 

 the cells acted upon by the sun's rays looked 

 shrunken, exhibited irregular contours, and the 

 plasma was drawn together in lumps, chiefly in 

 the direction of the poles of the cells. 



Assimilation in Green Plants. — "Nature" 

 reports a new method of demonstrating the assimi- 

 lation in green plants, which Mr. Francis Darwin 

 recently communicated to the Cambridge Philo- 

 sophical Society. Farmer has shown that if an 

 Elodca leaf be subjected to a stream of hydrogen, 

 and be kept in the dark, its protoplasm ceases to 

 circulate. This stoppage depends on the proto- 

 plasm being deprived of oxygen ; the reappearance 

 of the movement is a consequence of the fresh 

 supply of oxygen yielded by the chloroplasts in 

 light. This action may be readily observed if two 

 or three Elodea leaves be mounted in water and 

 sealed down under a single cover-glass with a 

 preparation of melted wax and paraffin. If the 

 preparation be placed in the dark, the circulation 

 will quickly be affected by the want of oxygen, 

 and at the end of six or seven hours it will cease 

 altogether. It may, however, be restored by ex- 

 posing to sunlight or to the incandescent gas flame. 



Photo-Micrography. — At the last meeting of 

 the Royal Microscopical Society, Dr. H. Stringer 

 explained a novel invention for obtaining photo- 

 graphs of micro-preparations. The apparatus is 

 somewhat complicated in construction, but it 

 works readily and gives most perfect results. 

 During the course of the demonstration he took 

 several negatives of the germ that gives rise to 

 bubonic typhus and also of other bacilli. His 

 demonstration was received with much enthusiasm. 

 In a future issue we hope to be able to give further 

 details of the apparatus. 



Honours for British Microscopes. — The jury 

 of the Brussels International Exhibition of 1897 

 has awarded to Ross, Limited, ill, New Bond 

 Street, London, a Grand Prix, a Diploma of 

 Honour, and gold, silver and bronze medals for 

 their exhibits of optical instruments. 



Manchester Microscopical Society. — At the 

 November meeting of this Society, Mr. Mark 

 L. Sykes, F.R.M.S., read an interesting paper on 

 "Natural Selection in the Lepidoptera." After 

 dealing with the principles of natural selection as 

 set forth in Wallace's chart, he gave a number of 

 instances of mimicry in relation to tropical butter- 

 flies, specimens of which were shown in his collec- 

 tion, which was exhibited at the meeting. The 

 paper was also illustrated by lantern slides, which 

 had been prepared by Mr. A. Flatters, another 

 member of the Society. 



Mounting Aphides. — When mounting aphides 

 and other small insects, it will often be found that 

 the specimen has a tendency to curl its legs under 

 its body. This difficulty Mr. G. B. Buckton has, 

 in a measure, overcome, by first placing a few 

 drops of balsam on the glass slide, to which the 

 insect is then transferred by means of a moistened 

 camel's-hair brush. The efforts of the insect to 

 escape will cause it to spread out its legs in a 

 natural position, and a cover-glass may then be 

 placed in position and a drop of balsam placed at 

 the side, when, by capillarity, it will fill the space 

 between the slide and the cover-glass, and the 

 limbs will be found to have remained extended. If 

 three or four drops of the balsam are put on the 

 glass the wings may also be brought down and 

 caught to them so that they will remain expanded 

 in shape for examination. 



Society Transactions. — We learn from the 

 current issue of the " Transactions of the Edinburgh 

 Field Naturalists' and Microscopical Society " that 

 it is the intention of that society to revive the micro- 

 scopical section. This section has been dormant 

 for some years, but it was re-started last winter, 

 and, under the able directorship of Mr. W. C. 

 Crawford, M.A., F.R.S.E., it gives every promise 

 of doing useful work in the future. The members 

 of this section were last winter chiefly engaged in 

 working out the seaweeds and their freshwater 

 representatives. In a paper on " Plant Origins," 

 Mr. Crawford briefly indicates the main lines upon 

 which the work should be done. He is careful also 

 to point out that the mere collection, mounting and 

 naming should not be the one end and aim in view. 

 The subject has a philosophy. How these crea- 

 tures live, why they work, and their relations to the 

 great living cosmos, should all be sought for and 

 reasoned out. 



Diatoms in Stomachs of Oysters. — The exami- 

 nation of the stomachs of oysters and of other 

 molluscs will, as a rule, well repay the diatomist. 

 The following is Mr. G. Sturt's method. Pick out 

 the stomachs and drop them one by one into a 

 flask which contains, say, five or six ounces of 

 nitric acid that has been heated to boiling-point. 

 When they are all dissolved add an ounce of 

 hydrochloric acid and continue the boiling for five 

 minutes, dropping in at intervals a little bichromate 

 of potash. Fill up the flask with hot water and 

 empty the whole into a large beaker, filling up 

 with hot water. Skim off the fat, wash away the 

 acid, and boil the residue in soap and water. If 

 this does not get rid of all of the organic matter, 

 boil in sulphuric acid and chlorate of potash. 



