EFFECTS OF CARBON DIOXIDE ON PROTOPLASM. 25 



tion in the case of Amccba. It has repeatedly been urged by L. 

 Loeb ('02), ('20), ('21), etc., that amoeboid movement is due to 

 changes in protoplasmic consistency. Hyman ('17) has also ex- 

 pressed the same view. The fact that carbon dioxide has been 

 shown to cause such changes in the cases just described, and the 

 additional consideration that it must be produced in an amoeboid 

 cell at a rate that varies greatly with circumstances, give some 

 grounds for the hypothesis that the agent chiefly concerned in 

 bringing about the protoplasmic changes underlying amoeboid 

 movement might be none other than this substance. 



To determine to what extent the formation of pseudopodia can 

 be influenced by carbon dioxide, an extremely fine capillary was 

 made through which CO 2 -saturated water could be discharged in 

 small amounts. On several occasions quiescent amcebas (belong- 

 ing to a species similar to, but probably mot identical with, A. 

 Proteus') were found, and on gently discharging a^very small 

 amount of the solution of CO 2 against the body of the animal 

 pseudopodia were immediately put out in the direction of the 

 capillary. On at least eight other occasions a small amount of the 

 solution was discharged against the hindmost portion of a creeping 

 amceba. In every case the same result was obtained. Pseudo- 

 podia were first put out at the point where the CO 2 came in contact 

 with the body, the currents in the other pseudopodia being for a 

 time reversed. Then as diffusion occurred and the full effects of 

 the CO 2 became apparent all movements ceased for a few seconds, 

 the animals remaining, as it were, congealed in the form in which 

 they happened to be when overtaken by the effects of the dissolved 

 gas. This paralysis then quickly passed away and movements 

 were resumed in the original direction. To all appearances at 

 least the animals had undergone a local liquefaction followed by a 

 more general solidification. It follows from these rather crude 

 experiments that if the external application of CO., can produce 

 such results, it is not unlikely that internal effects of the same sort, 

 resulting from varying rates of metabolism in different parts of 

 the body, could conceivably give rise to amoeboid movements of 

 the usual type, though further work will be required to determine 

 how far such an hypothesis explains the observed facts. 



