^76 RESEARCH IN PROTOZOOLOGY 



a drop of liquid is placed on the vial over the specimen and cov- 

 ered with a coverglass. The cover may be temporarily held by 

 cedar oil or permanently cemented on with balsam. Better illumina- 

 tion is obtained by placing balsam or other liquid between the vial 

 and the slide. The vial may be permanently sealed to the slide or 

 kept separate. A flat vial can be employed or one can make vials 

 of various forms out of glass tubing. 



This method of preservation is serviceable for the intestinal 

 tracts of mosquito larvae or for any small object that can be made 

 to stick to glass. Large oocysts on infected mosquito stomachs or 

 any detail of the specimen not requiring very high magnification 

 can be demonstrated in these preparations. Several specimens may 

 be mounted in the same vial. The preservative can be changed at 

 will and if air appears in the vial it can be easily removed. If the 

 specimens come loose from the side of the vial they are not lost. 



The method of mounting in vials is designed primarily for un- 

 stained material, but one may use Schaudinn's or other liquid 

 fixative and subsequently wash, stain, dehydrate and clear the 

 specimen in the vial, finally filling the vial with liquid petrolatum. 

 Specimens may be stuck to the side of the vial by Schaudinn's 

 fixative (see method described below for fastening mosquito stom- 

 achs to sHdes). 



In case it is necessary to examine specimens under the higher 

 powers of the microscope, either sectioned or stained in toto, it is 

 advisable, of course, to fix them and eventually stain and mount 

 them on slides in balsam. 



Stomachs or salivary glands are dissected out before fixation. A 

 preliminary fixation on the slide makes them much easier to handle. 

 They may then be transferred by means of a needle or a small 

 camel's-hair brush to a watch-glass or vial where they receive 

 further fixation. They are then washed free from fixative and run 

 up tlirough increasing strengths of ethyl alcohol to seventy per 

 cent, where they may remain indefinitely. In case Schaudinn's 

 fixative is used, the stomachs or salivary glands may be trans- 

 ferred directly from the fixative to seventy per cent alcohol and 

 washed in several changes of this alcohol until free from the fixa- 

 tive. Add enough iodine (Weigert's or LugoTs solution) to one 

 of the alcohols to facilitate the removal of the mercuric chloride. 

 If the specimens are deeply stained in the iodine they may be de- 

 colorized by seventy per cent alcohol to which a drop of one per 



