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 



