266 



DAVID DAY WHITNEY 



Brachionus pala 



In August of 1908 a small pond was found at Cold Spring 

 Harbor, Long Island, New York that contained great numbers 

 of this species of rotifer. The pond was located in a small 

 sunny pig pasture in which .there were kept a few pigs. These 

 animals lay in the pond a large part of the time during the hot 

 days and consequently the water became somewhat foul and 

 furnished an ideal culture medium for the rotifers and the va- 



Diagram 1 Hydatina senta. Showing that a continuous diet of Polytoma 

 through a long period of time yielded only female-producing females but when 

 the diet was suddenly changed to Chlamydomonas male-producing females 

 appeared at once. P indicates a Polytoma diet, C indicates a Chlamydomonas 

 diet. 



rious micro-organisms on which they fed. No experiments were 

 carried out at that time but some mud from the bottom of the 

 pond was taken, dried, put into a paper bag, and stored in an 

 ordinary laboratory room. 



In February of 1915 some of this dried mud was put into a 

 solution of 10 cc. of bouillon and 140 cc. of tap water and placed 

 near a window. Within a few days various protozoa were nu- 

 merous in the jar and a few females of the rotifer, Brachionus 

 pala, were found. These females ujidoubtedly had hatched 



