FOOD AND PARTHENOGENETIC REPRODUCTION. 1 93 



King, also, in experiments with albino rats has found that 

 continued inbreeding of the rat, when subjected to a varied and 

 well balanced diet, does not weaken the race. On the contrary, 

 the strains were larger, more fertile, and lived longer than many- 

 strains of stock rats in which no inbreeding was allowed. Castle, 

 also, found after inbreeding the fly Drosophila (brother and sister 

 matings) for fifty-nine generations, that no apparent decrease 

 in the size and vigor, as compared to those with which he started, 

 was noticeable. Noyes has recently finished the 250th partheno- 

 genetic generation of the rotifer Proales decipiens and has detected 

 no noticeable decline in vigor. Moreover, males of this species 

 have never been seen. East and Jones are inclined to believe 

 that if proper changes in the diet had been made in the experi- 

 ments of Whitney and Shull upon the rotifer Hydatina senta that 

 the normal vigor of the races would have been maintained. 



Problem. 



The following experiments with the rotifer, Hydatina senta, 

 were begun in order to determine if possible whether the gradual 

 loss of vigor is due to the parthenogenetic reproduction or to a 

 too restricted diet. The various races used in these experiments 

 were kept under identical conditions as to temperature, light 

 and culture water. Race A was fed. a colorless Polytoma diet, 

 whereas race B was fed a diet consisting of the Polytoma plus 

 several kinds of green protozoa, predominately Chlamydomonas . 

 The plan has been to keep the races in a parallel series and to 

 study the effect of the two diets upon the two races. A third 

 race (C) which has been obtained from wild rotifer cultures in 

 the natural environment has been introduced into the series in 

 order that the rate of reproduction of the rotifers under restricted 

 and controlled environmental conditions might be compared 

 with the rate of reproduction of those under the uncontrolled 

 conditions of nature. 



Acknowledgment is due Professor David D. Whitney for his 

 suggestions and supervision of the work. 



Methods. 

 Some dried fertilized eggs of the rotifer, Hydatina senta, were 

 collected at Lincoln, Nebraska, on September 17, 1920. One of 



