74 Phylum Protozoa 



are present, the culture (minus the rice-agar) is added to a rice-agar 

 bowl with 30 cc. of culture solution A. The steps from here are the 

 same as before. 



The cultures were maintained at 19-2 2 ° C. by stacking the finger 

 bowls in a sheet metal container, placed in a sink through which tap 

 water was kept circulating to the level of the highest finger bowl. Even 

 better growth has been obtained at 17-19 C, but it was easier to main- 

 tain the former temperature. 



Arcella. The foregoing technique has also been very successful for 

 this organism. In this case, however, temperature control is not neces- 

 sary. 



It is detrimental to have Stentor, Paramecium, large hypotrichs, 

 Philodina, or Stenostomum in cultures of Amoeba or Arcella. A culture 

 in which these organisms have gained ascendance should be discarded 

 and precautions should be taken against contamination of other cultures. 

 Chilomonas and Colpidium while not detrimental in moderate popula- 

 tions, should not be allowed to proliferate to the point where a culture 

 becomes cloudy with them. Mold usually grows on and about the rice 

 and does not seem detrimental although at times it is annoying since it 

 is hard to disentangle the Amoebae from the mycelium. 



Actinosphaerium. For this organism best success has been obtained 

 by insuring the presence of Paremecium, Stenostomum, or Philodina, 

 which forms, apparently, serve as prey. To 30 cc. of solution A in a 

 rice-agar bowl add 30 cc. of a dense culture of either of these animals 

 and inoculate with 5-10 Actinosphaeriae. Maintain in diffuse light and 

 replenish with more of the above mentioned organisms as required. 

 Prolific cultures have usually been obtained in about two weeks. 



AMOEBA 



William LeRay and Norma Ford, University of Toronto 



THE fact is not generally appreciated that Amoebae are found in 

 clean water, not foul. Two forms of Amoebae {A. proteus type) are 

 used in our department. One of these, an unusually large and active 

 form, possessing many pseudopodia, is found in association with catfish 

 and newts (Ameiurus nebulosus and Triturus viridescens). Another 

 with fewer pseudopodia and more regular in outline is taken with the 

 Brook Stickleback (Eucalia inconstans). The latter form we find the 

 more satisfactory for class work. 



The Brook Sticklebacks are collected in the backwash pools of rivers 

 or streams. Two or three of these small fish are placed in a bowl con- 

 taining 2000 cc. of pond water and fed upon Daphnia or enchytraeid 

 worms. Gradually ooze forms on the bottom of the bowl and in about 

 two weeks this ooze will be found to contain Amoebae. 



