INVERTEBRATES 599 



sufficient to completely cover it, and arrange in any desired 

 position. Invert the cover-glass and float on to some chloroform ; 

 leave for half an hour or longer, according to the size of the drop. 

 The drop of celloidin should fall away from the glass. Transfer 

 to melted wax, and allow time for the wax thoroughly to ]:)ermeate 

 (twenty minutes is long enough for fleas and lice). The result 

 will be a small tablet-shaped mass of spongy celloidin impregnated 

 with wax ; this can be at once imbedded, or may be put away for 

 future use. (Professor Boycott informs us that he has never 

 left his preparations for more than two or three weeks at a time, 

 so that he has no data as to how long the same could be kept, but 

 they could probably be stored indefinitely.) 



1187. Carbon Bisulphide Imbedding of Insects, etc. Heidenhain 

 many years ago recommended carbon bisulphide as a medium for 

 imbedding in wax. The wax is dissolved in carbon bisulphide, and 

 dehydrated insects, cleared in carbon bisulphide, etc., are placed in some 

 of the fluid, which is allowed to evaporate at a gentle warmth. Subse- 

 quently the material is rapidly treated in pure wax in the thermostat. 

 This method certainly curtails the length of time in the thermostat, and 

 overheating is a serious matter when one is working at chitinous or 

 brittle organisms 



1188. Techniques for Small Arthropods. Dr. A. D. Imms 

 informs us that for mounting and clearing aphids and other small 

 insects, etc., the following formula as used by Professor Berlese 

 for Acarina gives good results : — 



HoO 20 c.c. 



Chloral hydrate .... up to 160 grm. 



Gum arable * . . . . . 15 ,, 



Glucose syrup ..... 10 c.c. 



Acetic acid . , . . . 5 ,, 



The living specimens may be placed direct on the medium on the 

 slide, or may be killed by a short immersion in 10 per cent, acetic 

 acid, or boiling water. If the specimens are in alcohol they should 

 be washed in 10 per cent, acetic acid before mounting. After the 

 cover-glass is put on, gently warm the slide, then allow to cool, 

 and leave for one or two weeks to dry and set. Ring the slide 

 with a waterproof substance and finally ring with a layer of 

 Canada balsam. 



Gatenby kifls in 90 per cent, of absolute alcohol, leaves for a 

 few days, and mounts in Euparal (see § 488). 



Gum Chloral. A mountant for insects, etc., used in British and 

 other museums. We do not know original source. 



Distilled water ..... 50 c.c. 



Gum arable ..... 40 grm. 



Glycerin ...... 20 c.c. 



Chloral hydrate .... 50 grm. 



* Dissolve the gum in the water first, add the glucose synij), then eidoral 

 hydrate to saturation. Note that this mountant contains no glycerin 

 (see § 455). 



