Chemical Papers. 45 



water weakly acid. It has been shown also by them that the 

 metabolism in paramoecium, as in other animal cells, produces CO2. 

 Let us now place quite a anumber of paramoecia on a slide and 

 watch their movements. In a short time they collect in groups. 

 Is this due to a social instinct ? Because paramoecia are attracted 

 by any weak solution which gives an acid reaction, it seems obvious 

 that the congregation of the paramoecia is due to a formation of 

 CO2 by the metabolism of their bodies. 



If we try another class of chemicals, those of an alkaline reac- 

 tion, we find that they repel. 



The effect of immersion in different chemicals varies. In a one- 

 per-cent. solution of NaCl, the organisms revolve about on their 

 short axis and then dart from one part of the drop to the other. 

 This restless activity is followed by short periods of rest. 



A one-per-cent. solution of MgCl2 does not produce so great a 

 stimulation. Paramoecia, when immersed in this solution, dart 

 back and forth for a short time, but soon quiet down and act nor- 

 mally. According to Jennings, paramoecia swim about in KI solu- 

 tion for six or seven minutes, giving the characteristic reflex action. 

 This movement is followed by a continuous spinning which lasts 

 for several minutes. 



Curare produces a weakening effect after the stimulation, which 

 lasts for about fifteen minutes. In this solution they alternate, 

 running back and forth and spinning about, and finally become 

 extremely quiet. 



By these few examples we see how differently some chemicals 

 affect the animal than do others. Some produce a prolonged back- 

 ward movement, some produce a continued spinning, and others 

 cause various modifications and combinations of these two move- 

 ments. 



Organic chemicals, such as sugars, gelatin, and urea, do not act 

 on the motor reflex, but distend the infusorian and cause protru- 

 sions to arise on the exterior of the animal. I have experimented 

 with sugar and gelatin. In connection with experiments with 

 sugar a very interesting thing happened. I had a large ciliate 

 which had been encysted for about nine months. After having 

 tried several different methods to induce it to come out of the cyst, 

 a solution of sugar was used. In about five hours the cyst had 

 burst and the contents had begun to swell. The animal did not 

 resume its active state, but immediately formed a new cyst. The 

 osmotic pressure of the sugar undoubtedly caused the cyst to burst 



