INVEBTEBRATA, CRYPTOGAMIA, MICROSCOPY, ETC. 1041 



process as simpler and easier than that of Dr. Hamlin, described on 

 page 507. 



With home-made punches of ordinary brass tubing (cartiidge 

 cases answer very well), cut out rings and disks a little larger than 

 the finished cells are to be, and fasten them to the sides by pressure 

 and gentle warmth, after centering as accurately as possible. Then, 

 with a tool made by bending a small chisel at a right angle about 

 half an inch from the edge, turn or scrape the cell on a turntable until 

 it is of the right size. If the tool is sharp, a beautifully polished sur- 

 face will always result. The chisels which accompany sets of brad- 

 awls are just right ; but any flat piece of steel, if not too heavy or 

 clumsy, will do. The cutting edge should be about one-fourth of an 

 inch wide. Punches, and all tools used for cutting wax, should always 

 be dipped or moistened in starch, prepared precisely as for laundry 

 use ; this operates much better than water, or indeed anything else. 



Atwood's Rubber Cell.* — Mr. H. F. Atwood calls attention to a 

 cell for opaque objects made of hard rubber highly polished. 



Fig. 112 is a sectional view of the cell, the dotted line indicating 

 the position of the thin glass covei*. The base is solid, 

 giving a black background of rubber, and round the top *^'^' ^ '"" 

 is a ledge fitted to receive a ^-inch cover-glass, which ^^^^----^^g^ 

 may be secured by a little shellac or similar cement. 



The cell is claimed to be specially advantageous in two ways : — 

 1st. It solves the problem which often perplexes the collector who is 

 crowded for cabinet room. Many objects for future reference may be 

 mounted, numbered, and put away without a slide, a cabinet drawer 

 holding 200, while but 40 slides could be accommodated in the 

 same space. 2nd. In exchanges the cells may be sent through the 

 post without glass slips, so that there is a saving in postage and no 

 risk of breakage. 



Mr. Atwood suggests that the cell " may be attached to a glass 

 slip by any cement before or after preparation." Our own experience 

 is that rubber is by no means easy to attach securely, and that some 

 other means of examining the cells under the Microscope will be neces- 

 sary. In this view, Messrs. Beck have devised a circular cell-holder, 

 in ebonite, holding 12 cells, which lies upon the stage, and can be 

 rotated so as to bring each cell successively under the objective. t 



Parkes's Frog-plate. - Instead of the ordinary method of examining 

 the circulation of the blond in the frog's foot, which is attended with 

 some degree of inconvenience, at any rate, to the animal, the following 

 plan is recommended; — 



Put the frog into an empty wide-mouthed bottle (such as a pickle- 

 jar), cover the cork witli a piece of linen rag, on which pour a little 

 sulphuric ether, and then insert the cork immediately, and lay the 

 bottle on its side. In a ft;w minutes the animal will be sufficiently 



• 'Sciencp,' i. (1880) p. 200. 



t A ilrscriptinn of tlii.-) hoMcr, with n flRurf, will !><• •^\\-cn in tho next iniml)or. 



