74 



SCIENCE-GOSSIP. 



sought for in its earlier stages, on its proper food 

 plant. This can be more often and more easily 

 accomplished than is commonly imagined, and besides 

 the procuring of good specimens of the perfect insect, 

 many useful and practical results may reward those 

 who take the trouble thus to investigate the life 

 histor)' of species. Many problems respecting the 

 value of varietal forms and aberrations may be solved 



by rearing butterflies. As an example of this I will! 

 conclude by instancing the case of Thais medesicaste 

 var. hotioratii. This was once gravely considered a 

 possible species, but Mr. Nicholson and others who 

 have reared numbers of the larvae of T. medesicaste- 

 have proved honofatii\.a be devoid of specific value. 



( To be continued. ) 



COLLECTION AND PREPARATION OF FORAMINIFERA. 



By Arthur Earland. 



i^Continjted /roiii page 54.) 



'T~*HE Gault of Folkestone is one of the richest fossil 

 ■*- formations as regards variety of foraminifera, but 

 the various Zones into which it has been divided vary 

 greatly in the nature and numbers of their foraminifera, 

 the Upper Zones being the richest. Without geolo- 

 gical knowledge or a competent adviser, the collection 

 of fossil cla}'s is always more or less of a speculation, 

 but speaking generally the greatest number of forami- 

 nifera will be found in the neighbourhood of sandy 

 partings or pockets in the clay. 



While the Gault is more or less foraminiferous, 

 through the whole of its thickness, the London Clay 

 is practically destitute of them. Personally I have 

 never succeeded in obtaining foraminifera from the 

 London Clay, although I have washed material from 

 a number of localities. There is, however, a well- 

 defined Zone running under London in which they 

 may be found, and possibly some readers may be 

 more fortunate. At any rate, the Excavations now 

 being made for the construction of the new railways 

 offer an opportunity such as may not occur again, for 

 procuring material from this formation. 



Some of the harder shales and softer limestones 

 and chalks which resist disintegration with water only, 

 may be broken down by the crystallisation of some 

 salt which has been absorbed in a fluid state. The 

 best salt for this purpose is acetate of soda, but good 

 results can be obtained with common washing soda. 

 The material is first broken up into small pellets not 

 larger than a hazel nut. These after being thoroughly 

 dried are dropped into a boiling .saturated solution of 

 the salt, which after boiling for a few minutes to 

 • allow of penetration, is set aside to cool. During the 

 cooling process the salt crystallises, splitting off the 

 outside la)'er of each lump in the act. On warming, 

 the soda dissolves again in its own water of crystalli- 

 sation, and the crystallisation is repeated over and 

 over again, until the lumps are broken up. The 

 resulting mud is then cleaned in the usual manner. 



In the Upper Chalk strata the chalk powder 

 obtainable from the interior of hollow flints yields 

 very fine foraminifera, often in the most perfect state 

 of preservation, though occasionally chalcedonised. 

 The small spherical flints which are common in some 

 localities yield the best supply of this chalk powder. 



A few hints in conclusion as to the treatment of the 

 cleaned material. Sift the cleaned material into as 

 man)' different grades as possible ; as it greatly 



facilitates the tedious work of picking over material 

 if all the grains are approximately of the same size. 

 Keep the material in bottles or tubes, tightly corked 

 and in a dry place. If kept in pill boxes, mould 

 will form on it sooner or later. Label every tube with 

 locality, etc., and never trust for this to memory. 



The foraminifera are best picked out with a fine 

 sable brush moistened by drawing through the lips. 

 They can either be mounted when picked out, or 

 transferred to covered cells, until required for mount- 

 ing. A short bristle lashed to the brush handle is- 

 useful for turning over material on the tray ; but it 

 should not be used for picking out specimens as they 

 are liable to drop off in transit. 



For spread slides a thin solution of shellac is the 

 best fixative. It is applied by means of the turntable, 

 and the forams must be placed on at once, before it 

 hardens. For mounting selected specimens I use gum 

 tragacanth, which is much superior to gtim arable,, 

 as it dries without glaze and is not so subject 

 to the variations of moisture in the air, as is gum. 

 arable. The gum should be made from the finest 

 powdered gum tragacanth, dissoh-ed in distilled 

 water. The powdered gum should be covered with 

 spirits of wine before the water is added. The spirit 

 keeps the particles apart and facilitates its solution. 

 A cr_\-stal of th)-mol, added to the spirit, will preserve 

 the gum from mould, or a few drops of clove or cassia 

 oil will answer the same purpose. The gum should 

 be of the consistenc)- of thick hone)-, and it need not 

 be spared in the mounting process, as it contracts and 

 becomes almost invisible in drying. A little of the 

 same gum diluted down to a clear liquid with distilled 

 water can be used for holding foraminifera in position, 

 when mounted in balsam. If carefully dried, the 

 gum will not show in balsam. 



Many fossil foraminifera and occasional specimens 

 of recent origin may be found having the interior of 

 the chambers filled with a mineral, pyrites or glau- 

 conite, thus furnishing perfect casts of the sarcode 

 body of the animal. The cast can be obtained by 

 slowly dissolving the calcareous shell of the foram by 

 means of dilute nitric acid, so weak as to be only 

 faintly acid to the taste. The casts can be removed 

 with a pipette and mounted opaque in the ordinary 

 way. 



28, Glenwood Road, 



Cat ford. S.E. 



