i6o 



HARDWICKE'S SCIENCE-GOSSIP. 



MICROSCOPY. 



Mounting Starches. — A. J. D. should have 

 warned persons who adopt his plan of mounting 

 starches that an excess of heat will cause the granules 

 to burst, and that if that should take place nothing 

 will be visible in the balsam. The safest plan is the old 

 one, that is to mix the starch with a little cold water, 

 place a drop of the mixture on the slip, and then let 

 it dry thoroughly. Before applying the balsam it 

 may be well to place a drop of turpentine on one side 

 of the i^atch. By tilting the slide, this will run into it 

 and facilitate the combination of the balsam. — J. Y. J. 



Preserving Fluid. — The recipe given by R. 

 Atkins is not very intelligible. What is "alkaline 

 nitrate of chlorine," and what " aniline com." ? 



The Crust on Teeth, — A great deal of informa- 

 tion on the subject will be found in a paper by Dr. 

 Arndt (Virchow's Archiv, i8?o, p. 76) who, amongst 

 the numerous other organisms (Bacteria, Bacilli, Vi- 

 briones, &c.) discovered Spirochete denticola, consisting 

 of spirally coiled threads about 0'0i-0"02 ^ in 

 diameter and 5-20 /i long. The number of 

 coils varies from I-IO, and they have a uniform 

 vermiform motion. The complete history of the 

 organism is at present unknown, but Dr. Arndt 

 regards it as probably a stage in the development of 

 true Bacteria. Mr. H. T. Butler in the " Proceedings 

 of the Royal Society," xxviii. p. 484, also describes his 

 examination of the fur on the tongue, of which 

 schizomycetes forms the essential constituent. The 

 slime around the teeth was found to consist of nearly 

 the same fungi. — Frank Crisp. 



Improved Zoophyte Trough. — Mr. J. J. 

 Howell's note, which appeared in the June number of 

 Science-Gossip, contains one or two errors which I 

 wish briefly to correct. I invented the trough in 

 question about three (not seven) years since, and after 

 sufficient trial brought it before the Liverpool Micro- 

 scopical Society. Some time afterwards it was 

 brought before the Royal Microscopical Society and 

 the Quekett Club (but not by myself), and was 

 figured in the Journal of one or both. Subsequently 

 an "improved" form of the trough, in which vul- 

 canite plates were substituted for brass ones, was 

 brought before the Royal Microscopical Society by 

 Messrs, Beck. I have not tried vulcanite, which no 

 doubt has advantages in some cases, as for instance 

 where marine organisms are under examination, but 

 for general use I prefer brass, as it allows thinner 

 plates to be used, and a flatter bevel consequently to 

 be obtained ; this is an advantage when higher 

 powers than the one-inch are used. The " improved" 

 troughs I find are fitted up with thick glass, which is 

 a mistake, as by using thin glass for both back and 

 front a half-inch objective will focus to the back of 

 the trough, and high powers, say up to the one- 



sixteenth immersion can be used to examine objects 

 on or near the front glass. Thin glass also allows a 

 much better dark ground to be obtained with para- 

 boloid or achromatic condenser. For keeping the 

 glass apart I have found the "extra thick" india- 

 rubber bands the most generally useful ; and in putting 

 the trough together care must be taken to have 

 india-rubber and glass perfectly dry, as otherwise 

 there is danger of a capillary leak and consequent 

 disappointment.— C7ia;'/i?j' Botterill, Liverpool. 



"Manual of the Infusoria." — Part iv. of this 

 invaluable work to microscopists has now appeared, 

 and there is no doubt that each instalment raises its 

 reputation in the opinion of competent judges. This 

 part brings the letter-press up to page 576, and, 

 like all former parts, it contains eight large and ex- 

 quisitely-finished plates, on which are displayed about 

 four hundred figures of Infusoria, in addition to 

 woodcut illustrations distributed through the text. 

 We heartily congratulate author and publisher on 

 the success of tliis great undertaking. 



" The Northern Microscopist." — The June 

 number of this ably conducted magazine contains 

 several capital articles on "Aerial Spores" (illus- 

 trated), "Double Staining," and very full notes of the 

 proceedings of the northern microscopical societies, 



" Portfolio of Drawings." — We have received 

 No. 5 of Mr. Thomas Bolton's admirable series of 

 drawings, accompanied by short life-histories of the 

 microscopic objects he is in the habit of sending out 

 to his clients. They include Protococcus nivalis, 

 Ophrydiurn, Clava squamata, Syncoryne fridescens, 

 Caprella lobata, Bowerbankia imbricata, Fedicellina, 

 Alcyonidi^tni, Sec. 



ZOOLOGY. 



The Skeleton Wheel-bearer. — Your corre- 

 spondent Mr. Ro.seter, in sending you the description 

 and sketch at p. 112, SciENCE-GossiP, May, i88i,has 

 quoted Cooke's "Ponds and Ditches," and in doing 

 so has copied a mistake in that work. The references 

 to notes 2 and 3 at p. 170 of " Ponds and Ditches" 

 should be reversed ; it will then be seen that the 

 skeleton wheel-bearer is a Dinocharis, of which Cooke 

 mentions two species, "Z>. Focillum" a.nd " D. 

 delraclus," whileCeTa.to]phyllnm, orhornwort, is a weed 

 among which these small Rotifera are found. If the 

 note (2) against hornwort in text be altered to (3), 

 and the note (3) to (2), it will be right, but SciENCE- 

 GossiP should have the correction also, as there is no 

 such Rotifer as Ceratophyllum. — G. D. Brawny 

 Ealing. 



Parasite or Hydra. — In reference to the para- 

 graph in the May number of Science-Gossip 



