328 D. D. WHITNEY. 



CHEMICALS. 



Professor Calkins was able to stimulate his weak races of 

 paramoecia by diabasic potassium phosphate and also by the 

 extraction of various glands and organs of certain mammals. 

 Different percentages of diabasic potassium phosphate, extrac- 

 tions of the thyroid glands of the cat and sheep, of the thymus 

 and adrenal glands, of the pancreas, spleen and liver, of the cat, 

 Liebig's beef extract, and alcohol were added to the culture 

 water in the watch glasses in which the rotifers were living. 

 Only negative results were obtained. 



DEATH OF THE PARTHENOGENETIC RACE A , AND ITS PROPORTION 

 OF MALE-PRODUCING FEMALES. 



Race B died out in March, 1911, in the 384th parthenogenetic 

 generation, but race A was stronger and continued to reproduce 

 parthenogenetically until June 12, 1912, when during the first 

 hot weather the room temperature became higher than usual and 

 this race died out in the 546th parthenogenetic generation. By 

 its side was another unrelated race C in the 438th parthenogenetic 

 generation. The latter race survived, since it was stronger, as 

 is shown in Table I. Probably race A would have lived longer 

 if the temperature had been kept lower, but eventually it would 

 have died out, for at this time it took about four days for a 

 generation of 4-6 young females to be produced while at the 

 beginning of the experiments in October, 1908, it only took 

 i|-2 days. 



Shull states: "A progressive decrease in the proportion of 

 male-producers with long-continued parthenogenesis occurs in 

 some lines of Hydatina, perhaps in all." This may be true in 

 some races or lines of Hydatina, but it does not seem to be true 

 for all races, as Shull is inclined to believe. Table VII. shows the 

 proportion of male-producing females in the early and in the late 

 history of this parthenogenetic race A. The environment 

 probably was more or less different in the two periods from which 

 these data was compiled so no especial emphasis can be laid upon 

 the higher percentage of male-producing females that occurred 

 near the end of this race. The influence of the environment in 

 causing male-producing females to be produced has been pre- 



