12 E. J. LUND 



counts of the number of grains contained in each individual were 

 taken at the end of the experiment. 



Table 1 shows (1) that Bursariae living in the two different 

 cultures differ in the total amount of food eaten in the same 

 length of time. In other cases, of course, individuals from di- 

 verse cultures will give identical results so far as feeding is con- 

 cerned, while two or more different cultures may also differ to 

 a greater extent than the above table shows. Moreover, the 

 amount of food eaten by a given culture may vary at different 

 times. The greater the length of time of feeding (within certain 

 limits) the greater the total amount of food eaten. Not only 

 does the total amount of food taken differ in the two cultures, 

 but what is equally important, (2) the rate of feeding varies with 

 organisms from different cultures. This was observed in numer- 

 ous other experiments. Under some conditions the animals fill 

 their bodies quickly, while at other times this takes place slowly; 

 or only a small number of grains may be eaten. 



The facts are shown most clearly by the curves A and B, 

 figure 2, representing the number of grains of yolk (ordinates) 

 eaten by the thirty individuals in successive periods of one-half 

 minute (abscissae) throughout the time of the feeding process. 

 Curve A is plotted from the results of culture A and curve 

 B from those of culture B, in table 1. The immediate rapid 

 rise of curve A shows that the rate of feeding of culture A dur- 

 ing the first six successive periods of one-half minute each was 

 about from five to twenty times as great as in any of the subse- 

 quent fifty-seven minute intervals. A similar high initial rate 

 is also shown by curve B (culture B), but here the rise to the 

 maximum was not so steep and the rate during the first six half- 

 minute periods was only about from four to ten times the rate 

 during the subsequent fifty-seven half-minute intervals. 



In order to show more clearly that the results apply to the 

 individuals taken separately as well as to the averages for all 

 (i. e., to the cultures as a whole) the data may be arranged as 

 in table 2. As this table shows, at the end of sixty minutes 

 all but an insignificant number of animals from each culture 

 had eaten yolk grains: hence, the difference in the amount and 



