522 COLLECTION OF FORAMINIFERA. 



will subside ; and as the Foraminifera (in the present case) belong 

 to the latter category, they will be found at the bottom of the 

 vessel, almost entirely free from extraneous matter, after this 

 operation has been repeated two or three times. It would always 

 be well to examine the first deposit let fall by the water that has 

 been poured-away ; as this may contain the smaller and lighter 

 forms of Foraminifera. — But supposing that it be only desired to 

 obtain the dead Shells from a mass of Sand brought-up by the 

 dredge, a very different method should be adopted. The whole 

 mass should be exposed for some hours to the heat of an oven, and 

 be turned- over several times, until it is found to have been 

 thoroughly dried throughout; and then, after being allowed to 

 cool, it should be stirred in a large vessel of water. The chambers 

 of their shells being now occupied by Air alone (for the bodies of 

 such as were alive will have shrunk up almost to nothing), the 

 Foraminifera will be the lightest portion of the mass; and they 

 will be found floating on the water, while the particles of sand, &c, 

 subside. — Another method, devised by Mr. Legg, consists in taking 

 advantage of the relative sizes of different kinds of Foraminifera 

 and of the substances that accompany them. This, which is 

 especially applicable to the sand and rubbish obtainable from 

 Sponges (which may be got in large quantity from the sponge- 

 merchants), consists in sifting the whole aggregate through succes- 

 sive sieves of wire-gauze, commencing with one of 10 wires to the 

 inch, which will separate large extraneous particles, and proceeding 

 to those of 20, 40, 70, and 1 00 wires to the inch, each (especially 

 that of 70) retaining a much larger proportion of Foraminiferal 

 Shells than of the accompanying particles ; so that a large portion 

 of the extraneous mattei*s being thus got-rid-of, the final selec- 

 tion becomes comparatively easy. — Certain forms of Foraminifera 

 are found attached to Shells, especially Bivalves (such as the 

 Chamacece) with foliated surfaces ; and a careful examination of 

 those of Tropical seas, when brought home ' in the rough,' is almost 

 sure to yield most valuable results. — The final selection of speci- 

 mens for mounting should always be made under some appropriate 

 form of Single Microscope (§§ 34-37) ; a fine camel-hair pencil, 

 with the point wetted between the lips, being the instrument 

 which may be most conveniently and safely employed, even for the 

 most delicate specimens. In mounting Foraminifera as Microscopic 

 objects, the method to be adopted must entirely depend upon 

 whether they are to be viewed by transmitted or by reflected light. 

 In the former case they should be mounted in Canada-balsam ; the 

 various precautions to prevent the retention of air-bubbles, which 

 have been already described (§ 160), being carefully observed. 

 In the latter no plan is so simple, easy, and effectual, as the 

 attaching them with a little Grum to Wooden Slides (§ 155). They 

 should be fixed in various positions, so as to present all the 

 different aspects of the Shell, particular care being taken that its 



