24 Transactions of the Society. 



V. — On Mounting Rotifers and Protista in Canada Balsam. 

 By The Rev. Eustace Tozer. 



{Read December 16, 1908.) 



Some years ago, when experimenting with cell-life, it occurred 

 to me that if delicate organisms like Rotifers and Protista could 

 be passed through oils, mounting in Canada balsam would follow 

 as a matter of course. I found that they could be prepared for oil 

 by passing through absolute alcohol after being fixed and hardened. 

 1 now use various fixatives : osmic acid 1 p.c, picric acid, glacial 

 acetic acid, absolute alcohol, formalin 40 p.c. 



In February 1908 I exhibited at the Society's Meeting some 

 Rotifers prepared and mounted in balsam by methods I will describe. 



I have brought a series of slides to exhibit to-night, including 

 Brachionus (infested with Sporozoa), Hydatina, Floscularia, (Ecistes 

 stygis (extended from tube, and showing wreath of cilia), Pterodina, 

 Euglena, etc. They are double-stained and without shrinkage. 



I may say that the methods are exceedingly simple, and within 

 easy reach of the average worker. 



The Methods. — To get Rotifers in quantities I placed them in 

 shallow saucers covered with glass, away from direct sunlight. 

 Clean pond-water is best, and I put in Euglena for food. Success 

 depends upon a good supply of food. They breed rapidly, and may 

 be picked off the surface of the water with a penknife. 



Extending and Fixing. — One drop of osmic let fall on the water 

 on the slide suffices for many. This acid is essential for Acincta 

 and Actinophrys to fix the rods. 



Three drops of cocaine 10 p.c. added at intervals will answer for 

 many Rotifers. Others are amenable to picric acid added at intervals. 



Picric acid or cocaine fixes pseudopodia of amoeba?.. 



Formalin added slowly extends the jaws of small sea-worms. 

 Formalin vapour, manipulated with watch-glasses, is the best 

 fixative for flagellate zoospores and the monads of infusions. 



Glacial acetic acid differentiates the jaw-parts of Rotifers, re- 

 vealing the most minute structure. It is particularly useful for 

 the study of kinetic phenomena in Rotifer eggs. The Rotifers may 

 be left in it for eight hours before passing through the other pro- 

 cesses to be described. The only drawback is that unless carefully 

 applied it shrivels the cilia. (Glacial acetic acid must be first 

 washed out with alcohol.) 



When the Rotifers are transferred to the slide — extended and 



