XIII, C, 4 
Shaw: Microtechnical Methods 
245 
Working with Volvocaceae and other algae at Manila, I 
have not found the above specified procedure satisfactory. It 
was sometimes successful, but often the evaporation of the 
water from the glycerin was so slow that fungus mycelia devel- 
oped to the ruination of the specimens which were exposed to 
the air in shallow dishes, but protected from dust. And, 
usually, glycerin which has been concentrated becomes greatly 
diluted by absorption of atmospheric moisture on extended ex- 
posure to the air. I have secured satisfactory evaporation of 
the water from the glycerin for small quantities of material by 
the use of the desiccator, and for larger quantities by the use 
of the vacuum pump. But to provide for the suppression of 
fungous growth during early stages of evaporation, and on holi- 
days when the vacuum pump, located in the power house, is 
not in operation, thymol was added to the dilute glycerin. The 
glycerin solution was prepared by dissolving 0.9 gm of thymol 
in 9 cc of 95 per cent alcohol, adding the solution to 900 cc 
of distilled water and shaking, and finally adding 100 cc of 
glycerin and shaking again. While the thymol prevents fungous 
growth, it cannot be relied on to serve indefinitely in open 
dishes, for it seems to escape in the course of time. And pieces 
of thymol, to be of service, would need to be fastened below 
the surface of the liquid. In using the desiccator for the evapo- 
ration, it is preferable to have the material in vials with narrow 
mouths, or if it be in wide shallow dishes, to keep the dishes 
nearly covered to insure that the evaporation and concentra- 
tion be not too rapid. 
For concentrating glycerin containing from 2.5 to 25 cc of 
Volvocaceae wide-mouthed bottles of 250 cc capacity are used. 
Each bottle is provided with a rubber stopper with two holes. 
In one hole is placed a bent glass exit tube which does not 
extend below the stopper. In the other hole is placed a glass 
tube of which the lower end is drawn to capillary fineness. It is 
broken off until, by trial, a suitable nozzle is obtained. It 
does not extend below the bottom of the stopper. The upper 
end is filled with a plug of cotton just dense enough to serve 
as a dust arrestor. The specimens in dilute glycerin are placed 
in the bottle, which is filled with the solution up to the shoulder. 
The stopper with its tubes is inserted in the bottle, and the 
outlet tube is connected with the vacuum apparatus. In the 
system used the pressure varies, but averages about one-fifth 
of an atmosphere. When the vacuum cock is open the air jet 
from the capillary nozzle should produce a depression in the 
