104 



SCIENCE-GOSSIP. 



COLLECTION AND PREPARATION OF FORAMINIFERA. 



By Arthur Earland. 



(Continued from pages 54 and 74. ) 



"POR the successful preparation of the material,! 1 ), 

 ■*■ whether freshly gathered or not, it must first be 

 thoroughly dried, using a very moderate degree of 

 heat. Great heat has a tendency to crack the fora- 

 minifera, and also deprives the hyaline specimens of 

 their glassy transparency, turning them milky white. 

 After drying, the material is passed through a very 

 coarse sieve of 10 or 12 meshes to the inch in order to 

 separate the larger fragments, stones, mollusca, etc., 

 from the foraminiferous sand. Very few of our 

 British foraminifera, except the parasitic forms, 

 will be found among this coarse residuum, but it 

 should nevertheless be carefully examined with 'a 

 pocket lens for abnormally large specimens. If the 

 material, however, is from tropical seas or from deep 

 water, the coarse residuum will often be found to con- 

 sist very largely of more or less perfect foraminifera. 



If the quantity of sand is small, the collector may 

 proceed to float it without further preparation ; but if 

 a large quantity is to be dealt with, it will be found 

 advantageous to pass it through a succession of sieves 

 in order to separate the material into parcels of 

 varying sizes. This will be found to facilitate the 

 floating operations by ensuring that all the particles 

 are of approximately equal weight. 



The floating operations should be performed at a 

 sink, a liberal supply of water being required, and if 

 possible by daylight, as it is easier to judge how the 

 process is going on than by artificial light. The 

 .ripod (fig. 1), containing a sieve covered with the 

 finest gauze (120 mesh wire or preferably 150-mesh 

 silk) is placed in the sink, the gauze being first 

 thoroughly wetted to facilitate the draining away of 

 the water. The glass jar is then nearly filled with 

 water, and two or three tablespoonsful of sand 

 poured in. If the material is coarse the sand sinks 

 immediately, followed in the course of a few seconds 

 by the greater number of the foraminifera. If the jar 

 is held up between the eyes and the light, the falling 

 grains can be observed, and at the right moment the 

 bulk of the water containing nearly all the forams in 

 suspension is poured quickly into the sieve from which 

 • the water drains away. The purity of the material 

 gathered in the sieve depends entirely upon the 

 judgment with which the operator has timed his 

 actions ; but practice is all that is required to obtain 

 good results. The residuum left in the glass jar will 

 still contain many foraminifera, principally those 

 specimens which are too heavy to float. This is 

 washed out into a large basin or jar for later treat- 

 ment, and the previous operation repeated with a 

 fresh supply of sand, until the " first floatings " have 



(') By an unfortunate oversight of the printers, 

 this portion of Mr. Earland's article was omitted last 

 month. It should be read on from end of p. 54 

 (ante).— (Ed. S.-G.) 



been separated from the whole of the material. The 

 time allowed for subsidence will of course vary with 

 the size of the particles, so that in the case of the finest 

 grades of material it may amount to a minute or more. 

 The actual time can only be settled by the judgment 

 of the operator, who must decide by watching the 

 falling material in a strong light. 



In the case of the finest siftings of sand the tension 

 of the surface film is so great, that unless the particles 

 are thoroughly wetted the sand grains float as readily, 

 or rather take nearly as long to sink, as the foramini- 

 fera. This difficulty may be overcome by shaking up 

 the contents of the jar, covering up the top with one's 

 hand to prevent the water splashing out, or even by- 

 putting the sand into the jar before filling up with water. 



When the whole of the material has been treated 

 in the manner described and illustrated on page 

 54 in July Science-Gossip the foraminifera 

 may be extracted from the residuum which 

 had been put aside in a jar, and which will be 

 found to consist almost entirely of sand. Take 

 a flat dish or pan with fairly straight sides, and 

 a spout. A half-plate photographic developing dish 

 answers as well as anything I know. Into this put 

 about a teacupful of the sand, covering it to a depth 

 of about three-quarters of an inch with water. If the 

 dish is then gently rocked with- combined up and 

 down and circular motion, the foraminifera will rise in 

 suspension in the water. By careful manipulation 

 they may be worked towards the corner of the dish, 

 when a sharp tilt empties them into the sieve. The 

 operation should be repeated two or three times, until 

 the whole of the foraminifeia ha\;e been separated 

 from the sand, which after a brief inspection, to 

 ensure that no specimens of importance are left in it, 

 may be thrown away. 



The material has now become very much less in 

 bulk, the reduction depending upon the amount of 

 sand included in the original gathering. The 

 contents of the sieve which I may call "First 

 Floatings," though consisting principally of foramini- 

 fera will be found to include organic and inorganic 

 debris of many kinds ; such as fragments of mollusca, 

 bryozoa, hydrozoa, ostracoda, sponges, seaweed, coal 

 and coke dust, mica, etc. If the material is intended 

 for study and selection only, the cleansing process 

 need not be carried any farther ; but if it is intended 

 to be mounted as spread slides, it will be necessary to 

 eliminate the greater part of these foreign substances 

 by a further process of floating, or in some cases by 

 repeated flotations. 



The first floatings should be thoroughly, but slowly, 

 dried, and a few teaspoonsful stirred up again in the 

 glass jar which should be filled with water almost to 

 the brim. Some minutes having been allowed for the 

 material .to settle, the floating portions may he 



