I98 W. V. LAMBERT, W. S. RICE, AND H. C. A. WALKER. 



wild race of rotifers, race C, were started. They were reared 

 under identical conditions with the A and B races and the 

 counts were carried over a period of three generations. The 

 average number of young produced by these mothers in 46.3 

 hours was 3.53. A complete record of the results of this obser- 

 vation can be seen in Table III. 



The two parthenogenetic races were then carried on parallel 

 with one another until the beginning of the 79th generation at 

 which time a fourth series of observations was started. 



During this fourth series of observations the A race produced 

 an average of 7.46 daughter-females while the B race produced 

 8.29. Very little variation occurred throughout the different 

 generations during this series of observations. A complete record 

 of the results of this observation is given in Table IV. 



Table IV. 



The two races were then carried on for thirteen generations 

 before another series of observations was made. The average 

 number of hours between counts in this series of observations 

 was 65.33 hours, the increase in length of time being due to the 

 slowness of reproduction which was probably caused by the low 

 temperature of the laboratory. The average number of young 

 daughter-females produced during this series by race A was 3.32, 

 while the number by race B was 5.15. A complete record of 

 the results of this series is given in Table V. 



The two races were again carried on parallel with one another 

 until the beginning of the 106th generation. At this time they 

 showed a very great degree of uniformity between the different 



