132 Phylum Protozoa 



STYLONETHES STERKII* 



BOTH protective and reproductive cysts of 5. sterkii remain viable 

 when dried. This discovery made possible a transfer of the new 

 hypotrich from Plymouth, England, to Stanford University, where the 

 strain was continued. 



The following wheat infusion method of culturing was used exclusively. 

 Twenty grains of wheat were cracked and then boiled in 15 cc. of glass- 

 distilled water for from 3 to 5 minutes. The fluid containing numerous 

 starch grains was used immediately after cooling and was transferred 

 to the culture by means of a pipette having a bore of 1.5 mm. 



Experiments have shown that thriving cultures are most easily main- 

 tained when complete evaporation of the medium takes place at inter- 

 vals. Consequently, the organisms were grown in watch glasses holding 

 conveniently about 4 cc. of fluid. These were ordinarily enclosed in 

 petri dishes to prevent evaporation and to facilitate handling, but when 

 mass encystment and complete evaporation of the medium was desired, 

 the cover was removed. Or, the cover may be partly removed so that it 

 protects the watch glass from dust but leaves a wide open gap between 

 the two dishes. Within 8-10 hours, at a temperature varying from 15- 

 22 C, the cultures were completely dried out. 



New cultures were started daily when free-swimming individuals 

 were wanted for study. By means of a mouth pipette 20 organisms 

 from a thriving culture were transferred to a watch glass containing 

 4 cc. of tap water and a drop of fresh wheat infusion. A drop of infusion 

 was added daily to old cultures until protective cysts began to appear 

 (2-4 days). Then they were allowed to dry out. Thus it may be 

 arranged that there are always on hand about as many new cultures as 

 old ones, and a reserve supply of dry cysts. If the study of active or- 

 ganisms is to be suspended for a few days or weeks, it is safe to rely upon 

 the stock of dry cysts to begin new cultures, as was proved by the trans- 

 fer of cysts in watch glasses from England to California. These cysts 

 were about 3 weeks old when they arrived. Excystment occurred in 3 to 

 4 hours after distilled water or tap water had been added. 



M. E. D. 



Order peritrichida, Family vorticellidae 



A METHOD FOR INDUCING CONJUGATION WITHIN 

 VORTICELLA CULTURES 



Harold E. Finley, West Virginia State College 



Materials: Columbia culture dishes, depression slides, culture tubes, 



* Abstracted from a paper in /. Mar. Biol. Assoc. 19:707, 1934, by Laura Garnjobst, 

 Stanford University. 



