308 



ROBERT T. HANCE 



The second method employed, though not so accurate as the 

 first since only one observation per vacuole per animal was 

 obtained, gave results which are approximately the same as the 

 first. The time of contraction was taken with a stop watch 

 from the instant the vacuole disappeared until it disappeared 

 again. With animals 'possessing three or more vacuoles two 

 watches were frequently used as the paramoecium would often 

 dry up if each contraction was timed separately. The results 

 obtained at each temperature are given below. The figures are 

 based on observations of thirty-five paramoecia. 



The well known fact that the rapidity of vacuole contraction 

 increases with the temperature is again brought out in these 

 tables. It is evident in the multi-vacuoled race that there is a 



Multi-vacuoled race. Time in seconds; tempei-ature in Centigrade 



