SCIENCE- GOSSIP. 



piece £6, or with racked sub-stage 25 shillings 

 extra. The addition of an Abb§ condenser adds 

 a further 25 shillings. The objectives supplied 

 with the stands are a f-inch of N.A. 26, and a i-inch 

 of N.A. 65, priced at 25 shillings and £2 respec- 

 tively. Both of these are excellent lenses, of good 

 definition, and arranged so as to work approxi- 

 mately in the same focal plane when rotated on a 

 nosepiece. 



EXTRACTS FROM POSTAL MICROSCOPICAL 

 SOCIETY'S NOTEBOOKS. 



[These extracts were commenced in the Septem- 

 ber number at page 119. Beyond necessary editorial 

 revision, they are printed as written by the various 

 members. — Ed. Microscopy, S.-Gr.] 



Notes by F. Phillips. 



The twelve diatom slides referred to in these 

 notes will probably form a pleasant change. 

 Diatoms are a family of confervoid algae of very 

 peculiar shape They are found in almost every 

 pool of fresh, brackish, or salt water, sometimes 

 forming a yellow or brown layer at the bottom of 

 the water ; at others, attached to various plants, or 



few washings, then treat in a similar manner with 

 nitric acid ; wash repeatedly with distilled water 

 until perfectly free from acid. Separate the various 

 diatoms according to their different specific 

 gravities by allowing them to pass through water in 

 the following manner : — Take along glass tube, about 

 two feet in length and half an inch in diameter, fitted 

 at the bottom with a stopcock to facilitate the 

 letting out of some of the diatoms at any stage of 

 the process ; place a drop on the slide and examine. 

 If suitable for mounting, proceed as follows : — Fix 

 a needle obliquely through a collar of cork which 

 is itself fitted to a low-power objective, and to the 

 end of the needle cement a bristle, preferably one 

 from a rat's tail. The end of the bristle can now 

 be focussed along with the diatom, and brought in 

 contact with the latter. The diatom will adhere 

 to the bristle, and can be raised and transferred to a 

 clean slide. In this manner any single diatom can 

 be selected out of a gathering and mounted sepa- 

 rately. Of course great care and patience are requi- 

 site, but practice and perseverance in this, as in 

 everything else, will bring good results in course 

 of time. The following brief description of the 

 characteristics of the individual slides may be of 

 further interest : — 



I. 



4. 



uouvvLfry 2 a oLubc 



j^,,a ^«.r ff 



jb u-tASzesitc*- s 6tcct*a*<t Vt 





•J ,Dbj. iMouy/fftf 



i.f 



frh 



?n<**, /£?*,• 



*f- 



Diatoms 

 (From Drawings by Miss F. Phillips.) 



on stones and decaying plant-stems — in fact in 

 almost any moist place. The individual cells are 

 called frustules, and are furnished with a coat of 

 silica, noteworthy on account of its beautiful mark- 

 ings, which take the form of bands or lines, either 

 parallel, radiate, or crossing each other ; also of 

 dots. These markings however cannot be seen 

 until the diatoms have been properly cleaned. 

 When the diatoms have been collected, one of the 

 most troublesome operations is freeing them from 

 impurities. Several text-books give different 

 methods, but the following is the one I adopt. 

 Place the diatoms in a test-tube with strong hydro- 

 chloric acid and boil for five minutes ; after allow- 

 ing the boiling to subside, get rid of the acid by a 



Campy iodiscus costatus (fig. 1) : frustules saddle- 

 shaped and contorted, valves circular with radi- 

 ating channels, the centre minutely dotted ; found 

 principally in boggy pools. Surirella striatula 

 (fig. 2) : frustules somewhat wedge-shaped, margins 

 produced into a kind of wing with distinct and 

 parallel channels, valves ovate and striate ; found 

 in brackish water. Navicula firma (fig. 3) : valves 

 narrow, gradually tapering to the rounded ends, a 

 longitudinal line near each margin, central nodule 

 conspicuous, striae fine ; common in ditches. 

 Istlvmia enervis (fig. -4) : frustules depressed, valves 

 of a reticular or cellular appearance, uniformly 

 covered with depressions ; found in salt water 

 only. Coscinodiscus robustus (fig. 5) : frustules 



