64 



HA R D WI CKE ' S S CIE NCE-GOt^ SIP. 



William Browne also writes an amusing account 

 of a "Squirrel Hunt," in which he speaks of the 

 "dray" of the squirrel. Squirrels sometimes, even 

 in this country, have their coat of a much lighter 

 colour in winter than in spring, and various piebald 

 specimens are on record. 



George Dewar. 



MICROSCOPY. 



MiCROSConc Illumination. — I write to express 

 my indebtedness to Mr. F. Kitton for his suggestion 

 in your December number. I find the globe of water 

 vhich he uses for an achromatic condenser fully to 

 realise his description, and where there is a swinging 

 mirror to answer the part of a swinging substage, 

 carrying an achromatic condenser. I wish also to 

 remove two dii?iculties in the way of such as are de- 

 sirous of acting upon his suggestion. The first 

 serious difficulty I found, was in obtaining such a 

 globe — opticians and glass dealers could give me no 

 help ; at last an engraver gave me the address of 

 Messrs. Gray & Son, Clerkenwell (close to the 

 church), dealers in watchmakers' tools. There I found 

 several sizes of globes in stock, and purchased one of 

 7^ inch diameter. On mixing the copper sulphate in 

 tap water, I found the liquid cloudy within a few 

 hours of filtration. By the addition, however, of a 

 few drops of pure sulphuric acid, the cloudiness was 

 entirely removed, and the contents of the globe have 

 been perfectly clear ever since. — H. M. Stallybrass. 



How TO LABEL MICROSCOPIC SLIDES. — As little 



has been said of late about labelling micro, slides, 

 may I be allowed to recommend a plan which I 

 devised four years, ago and which I now use for the 

 whole of my collection ? Instead of one thin paper 

 label at one end of the slide, I use two labels and 

 make them of slips of thick card or millboard, I in. 

 long by J to J in. wide. These may be covered with 

 white paper, or the ordinary printed labels placed on 

 them. If the cards are sufficiently thick the slides 

 may be placed one against the other without fear of 

 damage, for the glass of one slide does not touch the 

 cell or cover of the next. Hence there is no need of 

 a cabinet in which to keep the slides as any box of a 

 suitable size will do. I use card boxes 3 in. deep, 

 with one side to open ; each box contains about two 

 dozen slides, and is labelled at the top with the class 

 of objects thus: "diatoms," " animal hairs," "geo- 

 logical," and so on. I have 400 slides labelled in this 

 way, so I speak from experience. Of course slides 

 so labelled can be put in cabinets of the usual kind, 

 if necessary. — G. II. Bryan. 



The Royal Microscopical Society. — Part i. of 

 vol. ii. of the Journal of the above society, just 

 published, contains papers by W. A. D. Michael, 

 F.L.S., on " British Oribatidx " ; by Mr. T. Charters 



"White, on "A new Growing or Circulating Slide" ; 

 and by Mr. W. H. Symons, on " A Hot or Cold Stage 

 for the Microscope " ; besides a copious and well- 

 arranged summary of matters affecting microscopy, 

 which is a new and improved feature of the new 

 editorship. 



Crystallised Fruit Salt. — It may not be 

 generally known to your readers that Eno's Fruit 

 Salt, when crystallised, makes a magnificent polari- 

 scope object. The mode of preparation I have 

 adopted is as follows : In a small test tube, say 3 in. 

 X 5 in., dissolve as much of the salt as would rest on 

 a sixpence, by adding distilled water to the depth of 

 an inch. With the end of a glass rod spread a few 

 drops of this solution over an ordinary 3 in. X i in. 

 glass slip, and in a few minutes crystallisation will take 

 place. The slide is now ready to be examined 

 under the microscope, and a selenite plate should be 

 added; it will then be seen to be covered with numer- 

 ous beautiful formations, each somewhat resembling a 

 Maltese cross made up of brilliantly-coloured needle- 

 like crystals. If the slide be held over the flame of a 

 lamp as soon as the solution is placed on (so as to 

 hasten crystallisation), the colours will be the more 

 splendid without selenite. Other beautiful effects 

 may be produced by the addition of a few drops of 

 alcohol to the test tube. The slides, as soon as dry, 

 may be mounted in Canada balsam. I trust many 

 may be induced to try these simple experiments, and 

 I can promise them a rich reward for their labour. — 

 George jfokn IVightniaii. 



ZOOLOGY. 



How do Eels breed ? — In reply to M. N. N. 

 G. C, I extract the following from "Blackwood's 

 Magazine" for January, which seems to be pretty 

 conclusive: — "Naturalists affirm" (says the writer) 

 " that the eel deposits its spawn as other fish do, and 

 state that the microscope reveals the presence of 

 spawn and milt in the eel. This is so much opposed 

 to all the statements and experience of eel-fishers and 

 eel-setters, that we cannot accept it as a fact ; and 

 after listening to so many eel-fishers who stoutly 

 affirm that they have constantly opened eels in 

 February which have been full of minute living eels 

 (not parasites), and that in a tub of eels young ones 

 have been found in the morning that were not there 

 over-night, we strongly lean to the theory that eels 

 are viviparous. To use their own words, there are 

 thousands and thousands of eel-fry all alive in the 

 bodies of eels cut open in February. The young fry 

 are contained in a membranous sac, as long and 

 thick as one's finger, and the eyes and backbones of 

 the fry are distinguishable. When the sac is cut 

 open, the fry unbend themselves and wriggle about. 

 Eels are found in this state during February, March 



