PREPARATION 21 



vial or on a slide. The specimens should remain in the clearer for 

 fifteen minutes or more. Where the specimens are to be mounted 

 in a nonresinous media as glycerin jelly, clearing is unnecessary. 

 The following substances can be used for clearing, chloroform, 

 xylol, cedar oil, oil of bergamont, benzol, turpentine, synthetic oil 

 of wintergreen, carbol-turpentine, carbol-xylol, and oil of cloves. 

 The last two give excellent results. 



The oil of cloves can be used after dehydration with com- 

 mercial alcohol. It differs greatly in shades of color, a light 

 colored oil should be used. Specimens cleared with clove oil become 

 very dark colored with age. 



One of the most practical clearers for use with coccids is 

 carbol-xylol. It can be used after commercial alcohol, clears 

 rapidly, evaporates slowly, and specimens do not discolor with age. 

 The solution is prepared by combining one part by measure of the 

 melted crystals of carbolic acid with three parts of xylol. 



If it is inconvenient to complete the preparation of the 

 specimens immediately, they should be removed from the caustic 

 potash, washed, and stored in alcohol. A stay of a few liours in 

 alcohol will not injure stained specimens, but a stay of two or 

 three days in alcohol or carbol-xylol does effect the intensity 

 of the stain. An examination of stained cleared specimens of 

 large individuals in a watch-glass is often very advantageous. 

 Such specimens should be placed in clove oil for study. If the 

 specimens are to be mounted after the completion of the exam- 

 ination, they should be placed in 95 per cent alcohol to remove 

 the clove oil and for dehydration and then cleared in carbol-xylol. 



Mounting. — The specimens after clearing are ready for mount- 

 ing in a resinous mounting media, as Canada balsam. They 

 in most cases are minute and the use of cover-glasses one-half inch 

 or twelve millimeters in diameter will be found more economical 

 of time when the specimens are studied. Several specimens, except 

 in the case of large species, can be placed under a single cover-glass. 

 The specimens should be arranged in a row, thus | | | | and 

 sufficient very thin balsam to cover them added. The balsam 

 should be allowed to harden for a short time and fasten the 

 specimens in place. When sufficiently hardened, add enough 

 balsam to fill the space under the cover and carefully put the 

 cover-glass in place. Do not use more balsam than is absolutely 

 necessary, the preparation must be thin if an oil immersion 

 objective is to be used. In order to secure thin preparations, the 

 balsam should be diluted until it is about as thin as water. If 



