62 CASPER 0. MILLER. 



some minutes before the vacuoles reappear and the zoospores 

 begin to feed again. 



It is not an infrequent experience that some protozoic forms 

 are killed by simply placing them in fresh water. The plas- 

 modia may not be as sensitive as the zoospores. They may 

 have sufficient vitality not to be killed by the treatment to 

 which Celakovski subjected them, but the writer questions 

 whether the results obtained under the conditions in his 

 experiment can be used as a basis for conclusions as to what 

 Plasmodia do in the fluids in which they thrive. His studies 

 also showed that the plasmodia did not digest the encysted or 

 active Colpoda which they had ingested. By the study of 

 plasmodia taken from hay cultures and placed on a slide with 

 a few drops of fluid containing Colpoda, the writer obtained 

 results which showed that they do digest Colpoda. 



The observations of Lister (44) also show that plasmodia do 

 take in microcysts, enclose them in vacuoles, and digest them. 



Observations on the Ingestion ofFo reign Substances 

 and the Multiplication of the Zoospores. 



Lister (30) described the taking up of bacteria by the 

 zoospores of Stemonitis fusca and Trichia fallax. The 

 bacteria were drawn in by pseudopodial prolongations, which 

 always came off from the posterior extremity, and were 

 carried to vacuoles near the nucleus, where they remained 

 until digested. He also gave them particles of carmine, which 

 were ingested but not digested. 



The zoospores of Stemonitis A, B, or C have not been 

 observed to put out pseudopodial prolongations and draw in food 

 particles, but the writer has seen the zoospores of Stemonitis 

 A, B, C, and Ceratium porioides take up bacteria and par- 

 ticles of carmine by means of a kind of vacuole which forms at 

 the surface of the body (fig. 12). It is situated most frequently 

 in the anterior half, but may form at any portion of the surface. 

 The formation of these vacuoles can best be studied in a culture 

 which has been on a slide for some hours. If a drop is taken 



