FOSSIL SPONGES, ETC. 31 



repeatedly ; allow this to stand for some time, and 

 then draw off the milky fluid with the siphon. Do 

 this again and again, until when shaken up the 

 bottle appears as if it were no longer full of a milky 

 fluid, but, when placed close to the eye against 

 a bright light, of small separate grains diffused 

 in the water. These are the treasures we are in 

 search of, but they have next to be separated from 

 the larger fragments of chalk which have not been 

 disintegrated by the scraping and shaking. To do 

 this shake up the bottle, and with the siphon im- 

 mediately draw over water and foraminifera into the 

 second bottle ; thus a certain portion of shells to- 

 gether with nearly all the water is drawn over. Allow 

 these to settle ; then draw off the clear water and 

 repeat the process until all or nearly all the shells are 

 in the second bottle, leaving the lumps, etc., in the 

 first ; then filter with blotting-paper, and dry in an 

 oven, when they will be ready for mounting. I reckon 

 about one pill-box full of foraminifera to a washing, 

 and store the preparation dry. Boil them in a test- 

 tube with turpentine, and mount in balsam. 



The more solid limestones of the Silurian or Car- 

 boniferous age, in which we suspect the presence of 

 foraminifera, must of course be treated in another 

 way. The student may frequently detect the pre- 

 sence of foraminifera by means of a good Coddington 

 lens. Thin chips of the limestone should be carried 

 away, ground on one side, mounted on glass, and then 



