ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 887 



the largest forms, some of which, as Nodosaria, Dentalina, &c, may 

 be nearly half-an-inch long. 



A large cup-full of the fine sifted powder must now be put into 

 the silk-gauze sieve, and a good stream of clear fresh water be allowed 

 to wash it until all signs of milkiness have disappeared, and the water 

 runs away quite clear, neither fingers nor spoon being used to stir up 

 the material, but letting the stream of water from an indiarubber 

 tube fixed to the water supply do all the work, directing it so as to 

 move the powder well about. When the water runs away clear, wash 

 all into a corner of the sieve, drain, and tip out the chalk powder on to 

 a plate to dry thoroughly in the oven. Repeat this process until all is 

 washed ; and when dry and cold sift into sizes for examination. The 

 finest siftings will probably be the richest in species. If the chalk- 

 powder is good and the washing properly done, a considerable portion 

 will be found to consist of Foraminifera, Ostracoda, sponge, and. other 

 spicules, the remainder being sand, &c. 



If sponge spicules or other siliceous organisms only are being 

 sought for, pour dilute hydrochloric acid over the chalk-powder, and 

 let it remain for a day or two to remove all the lime ; after which 

 pour off the acid, and wash well with clean water until every trace of 

 the acid is removed ; then dry, sift, and examine. 



As these Foraminifera are fossil and mostly siliceous they will not 

 " float," but the washed material must after drying be examined 

 under the Microscope and the individual shells picked out with a fine 

 miniature red sable pencil, and for doing which there is no royal road. 

 The best tray for the purpose is one made of black ferrotype plate 

 4 inches x 1^ inch with the edges on each side and one of the ends 

 neatly turned up about -^ inch, on which a layer of the washed 

 material is spread as thinly as possible, and the tray passed regularly 

 from right to left across the field. 



Directions are also given for dealing with fresh dredgings of sea- 

 mud, shore-mud ,&c, and with ship's soundings, where the Foraminifera 

 are mixed with tallow, lard, &c. 



Of all ways of mounting Foraminifera none is to be compared with 

 mounting them as opaque ; they look best without a cover-glass. 

 Ebonite rings should be selected of such sizes that one will just fit 

 inside the other, the smaller being cemented to the slide and the 

 larger to the cover-glass. 



Preparation of Diatoms.* — Prof. J. Brun describes the following 

 process which he employs for destroying the endochrome of diatoms. 



If the diatoms are fresh and wet, crystals of permanganate of 

 potash should be added, and 10 parts water for each 1 part of the salt. 

 If the diatoms are dry (pure or mixed) they should be wetted with a 

 little of the concentrated solution of the salt, having even crystals in 

 excess. The reaction of the permanganate should last about 12 hours. 



The mixture (placed in a 100 gr. phial) should be stirred occa- 

 sionally and put in the sun or on a warm stove. The phial should 



* Joum. de Microgr., vi. (1882) pp. 457-8. 



