FOEAMINIFERA. 27 



An excellent substitute for the sieve is a good^ 

 fine linen handkerchief {ivithout holes in it), stretched across a 

 colander so as to make a deep basin in it. The best material for 

 the sieve is miller's silk-gauze, i8o threads to the inch, which is 

 very strong and durable ; if fewer threads than this per inch, 

 minute forms will slip through and be lost. When the salt is 

 washed out, dry the sand perfectly, in any convenient way, and 

 allow it to get quite cold, after which it should be passed through 

 a fine sieve (No. 50 or 60), or a vejy fine gravy-strainer. The 

 " coarse material " which does not pass through the sieve should 

 be examined, as most of the larger forms, which would not 

 " float " in the subsequent process, will be found in it. 



The Foraminifera are separated from the fine, or sifted, 

 material, as follows : — 



Procure a deep vessel, holding about three or four pints, such 

 as a wz/;^^-bottomed (not flat) milk-basin, or a common two-quart 

 tin, with a lip, into which pour a cupful of the fine material, and 

 then fill with clean, fresh, cold water, up to about half-an-inch 

 from the top. Stir this well with a spoon, breaking all bubbles 

 which may arise, and then allow all to stand for one or two 

 minutes for the sand to settle. The Foraminifera, having their 

 chamberlets full of air, will be found floating on the surface of the 

 water like a scum, and may be easily poured into a filter by 

 tilting the basin towards the spout or lip, and gently blowing the 

 surface at the same time. A very little practice will teach how to 

 do this so as to remove, by this operation, little more than the 

 scum itself. The dij finger should then be gently carried round 

 the edge of the basin, with a sort of revolving motion (so as not 

 to crush the delicate shells), to remove those adhering to the side, 

 and these, by means of a " washing-bottle," or other gentle stream 

 of water, may be washed off the finger into the filter. Fresh 

 material may be added, and thus " floated " until all the gathering 

 has passed through the process. It is well not to let the basin get 

 more than half-filled with sand. Each cupful of this should be 

 well stirred up two or three times so as to secure all the shells 

 that will float, but of course the greater part floats with the first 

 stirring. It is desirable to float all the water off the sand through 

 the filter, so as to catch everything. 



The sand left in the basin may then be put on a soup- 

 plate, and should be well shaken, by slapping the outside with the 

 hand, which will cause most of the larger forms which have not 

 floated, and are still buried in it, to come up to the top, whence 

 they may be easily skimmed by means of a teaspoon. These 

 should be kept separate from the " floatings." 



The " floating " being finished, let the filter-paper drain to 



