RELATION OF BURSARIA TO FOOD 31 



A was now left to soak in its water for fifteen minutes longer, 

 this water was then drawn off and the yolk again washed twice 

 with water. Thirty individuals from the same material as used 

 above were now put into the dish. At the end of fifteen minutes 

 the following was the count: 



Experiment XII (h) 

 3, 1, 5, 1, 3, 4, 4, 3, 9, 3, 7, 3, 0, 4, 5, 3, 6, 0, 0, 4, 1, 4, 5, 0, 0, 2, 3, 1, 3, 1. Total 88 grs- 



This indicates that we may obtaiti the same result whether we 

 proceed with a strongly stained yolk and test successively after 

 each washing, or, as in the former experiment, by staining dif- 

 ferent portions of yolk to different degrees to begin with. This 

 was actually done in other experiments not given, and results 

 exactly similar to those in Experiment XII (a) were obtained. 

 To show that even a considerably stronger medium does not 

 injure the animals seriously, a yolk suspension stained with 

 saffranin more strongly than that used in A of Experiment XII 

 (a) , was made by leaving the yolk several hours in a very strong 

 solution of the stain. This was washed out several times and 

 then thirty individuals from the same culture material used in 

 the former experiments were put into it and left for fifteen min- 

 utes. They were then picked out and washed once in tap water, 

 and then transferred to an unstained yolk suspension for fifteen 

 minutes. The count gave the following (table 14) : 



TABLE 14 

 Experiment XIII 



MIXTURE NUMBER OF GRAINS EATEN BY EACH INDIVIDUAL 



Stained Oj 



Unatained 2' 3 



O! Oj 

 o' 0' Oi 1 







o' 3I 1 



2 

 2 3 2 8 



This shows that they were not injured sufficiently in even this 

 strongly stained suspension totally to prevent them from eating 

 unstained yolk immediately afterward. The cause of most of 

 the O's in the count is that, as the toxicity of the solution in- 

 creases, the organisms have a tendency to close up the oral 

 apparatus and do not open it again sufficiently, within the next 

 twenty minutes or so, to be able to take in the yolk grains. Of 



