EFFECTS OF CARBON DIOXIDE ON PROTOPLASM. 17 



after several hours another examination was made to determine 

 whether or not deaths had occurred. A considerable number of 

 experiments were made on FaraiiKrciitin. and as they all showed 

 a very satisfactory agreement in their general results, it will be 

 sufficient to describe in detail only the following typical one. 



The animals used in this experiment responded to centrifugal- 

 ization before treatment with CO 2 in the usual manner i.e., by a 

 partial, but by no means complete, separation of the food vacuoles 

 from the protoplasm when the force employed and the time of 

 exposure to it were as already mentioned. After the current of 

 CO 2 had flowed for one minute a slight increase in the readiness 

 with which separation occurred was noted ; this had decidedly in- 

 creased by the end of 5 minutes, and by the end of 10 minutes it 

 had become very striking. The India ink after centrifugalization 

 was now invariably found in a compact mass in the posterior end 

 of the body, so closely packed that the outlines of the individual 

 food vacuoles could scarcely be distinguished. The animals them- 

 selves at this stage of the experiment showed no visible injury 

 either from the exposure to the carbon dioxide or to the centrif- 

 ugal force. When placed in open watch glasses they not only 

 continued their locomotion in a normal fashion, but the food 

 vacuoles within a few minutes had become redistributed through- 

 out the cell and the animals had resumed their original appearance. 



After 15 and 20 minutes, respectively, from the beginning of 

 the experiment the results were essentially the same as those at the 

 end of 10 minutes, except that a swelling of the body was now 

 becoming increasingly apparent. At the end of 25 minutes a new 

 appearance could be noted. In a few of the individuals, although 

 the treatment was the same as before, the food vacuoles failed to 

 separate. The numbers of such animals gradually increased dur- 

 ing the next 15 minutes, until at the end of 40 minutes it was the 

 exception rather than the rule for such separation to occur, and 

 5 minutes later only a few showed any movements of the food 

 vacuoles at all. At 50 minutes this condition had become practi- 

 cally complete, and the protoplasm of the animals was now evi- 

 dently considerably more viscous than at the beginning of the ex- 

 periment. This increased viscosity or perhaps solidification 



