INFLUENCE OF GLANDULAR EXTRACTS. 27 



same pure line kept in the same physiological environment, and 

 (3) any significant diversity in the pulse rate of individuals from 

 a wild culture kept under approximately the same conditions in 

 the laboratory. Two pure lines A and B were started on a 

 depression slide, each being given 2 drops of distilled water and 

 one drop of I per cent, malted milk solution daily. On another 

 depression slide were placed drops containing individuals taken 

 from a wild culture. These were given the same diet. Both 

 slides were kept in a moist chamber at room temperature. On 

 the third and fourth days averages were made of the pulse rate 

 of four individuals from each group. It was found by repeated 

 experimentation that when the animals were fed at ten o'clock 

 in the morning they usually quieted down at about four o'clock 

 in the afternoon. Various futile attempts were made to quiet 

 them artificially without disturbing the pulse rate, but any 

 methods employed which increased the density or the pressure 

 of the surrounding medium definitely decreased the pulse fre- 

 quency. The individuals were kept on depression slides and 

 observed under both high and low power. By using a stop-watch 

 an accurate record of the pulsations could be kept. In all cases 

 the pulse rate of both vacuoles was taken, going alternately 

 from one to the other, and recording ten pulsations of each. 

 It would be unwise to observe ten contractions of one vacuole 

 before noting the other because of the rapid effect of any change 

 in physiological conditions. Tables I. and II. give the results 

 of the first series of experiments. 



From these records it is seen that the variability in pulse 

 frequency in different pure lines in not significantly greater than 

 the variability among individuals in a single pure line. Taking 

 the anterior vacuole, the average for pure line A is 3.9 seconds 

 more rapid than for pure line B, while the greatest variation for 

 any group within pure line A is 1.6 and for any group within 

 pure line B is 4.3. The same is true for the posterior vacuole. 

 The average for pure line A is 3.5 seconds more rapid than for 

 pure line B, while the greatest variation for any group within 

 pure line A is 1.8 and for any group within pure line B is 4.1. 

 For the wild culture the average of each vacuole presents approxi- 

 mate'y the mean average of the corresponding vacuoles of the 



