64 THE AMERICAN MONTHLY [March, 



these skeletons. Think, therefore, of the infinitesimal weight of each ; 

 nevertheless, though individually of so little account, materially the}- 

 have formed a mass in the Barbadoes iioo feet in thickness^ and 

 stretching for a considerable distance. 



Cut oft' now a piece about half an inch square and drop it in an 

 ounce or two of boiling water, to which has been added a few crystals 

 ofcarb. of soda, and let the material boil briskly for two or three 

 minutes, stirring once or twice with a glass rod. This will dissolve 

 the earth verv thoroughl}-. Put aside to cool and then fill a long test- 

 tube, or glass of about one-inch diameter, with water, and after shak- 

 ing the material in the cup pour a little of it into the glass. Let it set- 

 tle for 1=5-30 seconds and then pour oft" all but the sediment at the bot- 

 tom. Pour that sediment into a small ounce bottle and repeat the 

 operation. That will give you almost nothing but Radiolaria, and 

 further separation will get rid of most of the broken shells. Do the 

 same with another portion of the material and leave to settle for 1-2 

 minutes and then pour oft' as before. This will give you the smaller 

 and lighter forms also, but some dirt as well as broken shells. Clean 

 this still further, if necessary, and place in another ounce bottle. And 

 that is all the preparation that is needed to yield you excellent material 

 for study. There is nothing like the trouble about it that one finds in 

 cleaning the Richmond earth, for example, for diatoms. The skeletons, 

 by this simple process, are in fine order, except that the boiling has 

 possibl}' broken oft' some of the spines. If you want to save them, 

 boil the material less^ or use simply hot water to dissolve the material, 

 but in that case you will not get your forms so clean. A twelfth of an 

 inch, or even less, of the cleaned material is enough for a half-ounce 

 bottle. When this has well settled pour oft' half the water and add 

 alcohol as in the case of diatoms. 



Mounting. — Shake the bottle and take up a drop with the pipette 

 and evaporate on a cover-glass placed on ferrotype plate over the lamp. 

 Make a thin cell of rubber cement on the slide. Now dip the cover 

 in a little benzole to get rid of air-bubbles, drain oft' with blotting-paper, 

 add a drop of balsam, attach cover, and when the balsam is dry ring 

 with rubber cement, Brunswick black, or King's cement, and the thing 

 is done. Mr. D. B. Scott's method was to place the forms upon a slide, 

 with a considerable quantity of balsam in benzole or chloroform, and lay 

 the cover-glass over them. The balsam was then heated until the ben- 

 zole or chloroform boiled very briskly, after which the slide was allowed 

 to cool, and then finished as usual.* I mention it here for the sake of 

 those who may have some of the cleaned material dry. Where the 

 forms are kept in water, however, and the water evaporated over the 

 lamp, the subsequent boiling in benzole-balsam does not seem to succeed 

 very well ; at least this is my experience. Air-bubbles xvillforfn and re- 

 main., but by dipping the cover in benzole, after the forms are dried, 

 there will be no air-bubbles. A further advantage is that the forms are 

 dried on the cover, not on the slide, and that the forms, being in alcohol 

 and water, are more evenly distributed in drying than when boiled in 

 benzole-balsam, so that on the whole this method seems preferable, 



( To be continued. ) 



*See Jour, for Aug., 1883, p. 144. 



