Collecting and Preparing Foraminifera 217 



The residuum, which had been set aside in a jar, may 

 now be treated by the ' rocking ' process for the separation 

 of the remaining foraminifera. Taking the photographic 

 developing dish, or a tin tray may be used as a substitute, 

 enough of the residuum is placed in it to cover the bottom 

 to a depth of about ^ inch, and covered with about f inch 

 of water. If the dish is then rocked with a combined up 

 and down and circular motion, the foraminifera will rise in 

 suspension in the water, and by a little careful manipula- 

 tion may be gathered in one corner of the dish. A sudden 

 tilt will then empty them with the water into a sieve. 

 The operation should be repeated with two or three lots 

 of water, and the material left in the dish will then be 

 found to consist almost entirely of sand. The material 

 left in this second sieve, known as ' washings,' is not so 

 pure as the ' floatings,' for it contains a large percentage 

 of broken forms and shell fragments, coal-dust, and other 

 debris. It may be further purified, if desired, by being 

 dried and ' floated ' once or twice in the glass jar. 



If the floatings thus obtained contain much animal or 

 vegetable matter, as is sometimes the case, it is advisable 

 to boil them in a solution of caustic potash. This will 

 not damage the foraminifera so long as the boiling is 

 not carried on too long, and it effectually removes the 

 animal matter, which otherwise would encourage fungoid 

 growths. 



The processes already described are intended for recent 

 sandy gatherings. When the material is in the form of 

 dredged mud, it is first necessary to get rid of the finest 

 particles of this mud, for if the water is turbid it becomes 

 very difficult to judge the right moment for separating 

 the floating forams. The mud should be broken up into 

 small lumps, about an inch cube, and slowly but thoroughly 

 dried. It is then placed in a basin and covered with 

 water, which rapidly breaks it up into a fine mud. Such 

 specimens as may be observed floating on the surface of 

 the water may be easily removed by means of cigarette- 



