286 DAVID DAY WHITNEY 



THE INFLUENCE OF A SINGLE DIET 



In all of the preceding experiments there were used either 

 two diets, one of colorless flagellates alternated with one of green 

 flagellates or a mixed diet containing miscellaneous species of 

 protozoa, principally green flagellates. During the experiments 

 with the mixed diets when at times they consisted of nearlj^ 

 all of one species of flagellate, Chlamydomonas, it was suspected 

 that one favorable diet could be so manipulated as to yield either 

 female-producing or male-producing rotifers. In order to test 

 this hypothesis pure cultures of the green Chlamydomonas were 

 made in mixtures of bouillon and stable tea solutions. These 

 cultures were inoculated with the rotifer, Brachionus pala, 

 and several experiments were started and carried through to 

 completion. 



The flagellate, Chlamydomonas, passes through several stages 

 in its life cycle, some of which are to the advantage of the roti- 

 fers and others of which are distinctly to the disadvantage 

 of the rotifers as far as being of food value. In favorable cul- 

 ture solutions the individuals of Chlamydomonas are very active 

 during the sunny part of the day but do not reproduce very 

 much. However, at night, having reached their full size, many 

 of them become motionless and begin to divide inside of their 

 outer envelope. Here each divides three times resulting in 

 eight small individuals. Sometime in the morning hours the 

 parent envelope breaks and the eight young come out and soon 

 become separated from each other. These young individuals 

 are active during the day while increasing in size and at night 

 having reached their full size they become quiescent, begin to 

 divide, and before morning break into eight small individuals. 

 There is considerable variation in this life cycle. Some may 

 be in the eight-cell stage and break out in the early evening 

 while others may be in such stages in the late morning but the 

 large majority go through the cycle as indicated. 



When the Chlamydomonas are small in size they are the most 

 readily eaten by the rotifers. As they reach full size, although 

 they may be very active, they are not eaten at ail by the rotifers. 



