l6 M. H. JACOBS. 



capable of responding to this treatment (pigment and other gran- 

 ules and droplets of Arbacia eggs, chloroplasts of Spirogyra, cer- 

 tain fine granules in Colpldiwn) or such bodies could be introduced 

 in the form of food vacuoles rilled with India ink (Paramcecium 

 and Colpidium). The force used with the Arbacia eggs was esti- 

 mated at i, 600 times and with the other material at approximately 

 150 times that of gravity. The Arbacia eggs were centrifuged in 

 sea water, Spirogyra in pond or in distilled water, and the Protozoa 

 for the most part in their own culture fluid. 



A portion of the experiments here described were carried out at 

 the Marine Biological Laboratory at Woods Hole. The author 

 wishes to acknowledge his indebtedness to the Director, Professor 

 Frank R. Lillie, for placing at his disposal the facilities of the 

 laboratory during a part of the summer of 1920. 



EXPERIMENTS ON PARAMCECIUM. 



The procedure most frequently employed with this form was as 

 follows : The animals were first placed in a test tube with about 

 20 c.c. of culture fluid to which a few drops of a dense suspension 

 of India ink had been added. They were then allowed to stand 

 for 30 minutes, at the end of which time they contained numerous 

 black food vacuoles whose behavior could be followed with the 

 greatest ease. Before exposure to carbon dioxide they were tested 

 to determine the ease with which the food vacuoles could be sep- 

 arated from the remainder of the protoplasm. It was found in 

 all the experiments with the culture used that a two minutes' ex- 

 posure to a force of 150 times gravity caused a partial separation 

 i.e., there was a general tendency for the ink to move toward the 

 posterior end of the body but it did not by any means become 

 massed there, and in some individuals no movement at all was 

 evident. When, at the end of 30 minutes, the animals had formed 

 sufficient food vacuoles, a current of carbon dioxide was allowed 

 to bubble through the liquid containing them, and samples were 

 removed at intervals, immediately centrifuged for the same time 

 and at the same rate as before, and then examined in Syracuse 

 watch glasses. After this examination the watch glasses were in 

 each case exposed to the air to allow the escape of the CO 2 , and 



