RELATIONS OF BURSARIA TO FOOD 5 



In most of the expferiments the organisms were fed singly, 

 and large numbers were used, so that any individual variations 

 play a minor part, if any, in the final results. 



Where temperature regulation was necessary the experiments 

 were carried on in an oven kept constant to within 1.5°C. 



TO WHAT EXTENT CAN YOLK BE CONSIDERED A FOOD FOR 



BURSARIA 



As yet it has not become possible to propagate pure races of 

 Bursaria from single individuals, or in culture, by feeding it an 

 artificial diet of vitellin or fresh yolk; so that it must be re- 

 membered in conjunction with the facts presented at this time, 

 that the full requirements for the maintenance of life and re- 

 production have not been fully satisfied, and to this extent the 

 ideal conditions have not been met. 



But to prove that vitellin and fresh yolk are drawn upon for 

 the energy requirements and growth of the cell Experiment I is 

 given : 



Experiment 1 . Three sets of 74 individuals each were starved in tap 

 water for 24 hours. Set A was fed with fresh hard boiled yolk in suspen- 

 sion prepared as described above. Set B was fed vitellin ; while Set C was 

 not fed. Each individual in the three sets was left to eat as much as it 

 would in 20 minutes. They were then picked out and washed once in tap 

 water which had been boiled, from this they were removed to watch glasses 

 each containing 2 cc. of boiled tap water. The water was boiled in order 

 to kill any bacteria, or other organisms sometimes present in small 

 numbers in the tap water. Two individuals were placed in each watch 

 glass and these were set m. moist chambers which were kept side by side. 

 There was therefore no difference in the temperature at which the three 

 sets remained during the experiment, although a daily fluctuation in 

 temperature of 4 or 5°C. occurred. Such variation, however, does not 

 affect the results of the experiment for the particular end in view. It 

 was found that after feeding twenty minutes nearly all of those in the 

 fresh yolk suspension (A) had eaten large quantities, while those in the 

 vitellin suspension (B) had on the average not eaten so large a number of 

 grains as those in the fresh yolk suspension, although in both Set A and 

 Set B, each individual had eaten more than one grain. All the indi- 

 viduals in the three sets were treated identically except in feeding. 

 All were normal and active at the beginning of the experiment. At the 

 end of every 24 hours detailed records were taken for each individual, 

 as to whether it had a normal form or had undergone dedifferentiation — 



