DAVID L. CLAYBROOK 243 



manner. The point is this. Perhaps the animal needs to struggle 

 with its prey? This is, of course, a complete speculation but we 

 may be dealing here with a phenomenon on the physiological 

 rather than biochemical level. 



CLAYBROOK: I haven't tried any experiment which would 

 answer your question. 



LENHOFF: Didn't Hijdra grow well on frozen shrimp? 



CLAYBROOK: They grow at a reduced rate. 



LENHOFF: At a very reduced rate? 



CLAYBROOK: Not very reduced. But below that found with live 

 shrimp. The answer to this may also be leakage from the shrimp. 



LENHOFF: But they do grow on frozen shrimp. I would think 

 that this would answer Dr. Goreau's speculation l^y showing that 

 the struggling of live prey is not required. 



LOOMIS: It is interesting that apparently no carbohydrate is 

 necessary. In other words, pure protein is enough. 



CLAYBROOK: Let's say carbohydrate is not limiting at this state. 



LOOMIS: But you feed them solely on the 0-66% ammonium 

 sulfate fraction of liver protein? 



CLAYBROOK: This alone will not support continued growth. 

 This is only a specific assay for the heat labile factor. 



EAKIN: I think that some of you were not able to hear Dr. 

 Claybrook clearly when he described his method for demonstrating 

 the requirements of Hydra for the heat-labile factor. The Hydra 

 which he used as test organisms had been cultured at a sub-optimal 

 level of nutrition by feeding them on heated brine shrimp. The 

 response we studied was that of boosting them from this bare 

 maintenance level to that which we get when they are fed live 

 brine shrimp. 



LOOMIS: It is a specific assay for the heat-labile factor? 



EAKIN: That's right. Even the poorly growing controls are get- 

 ting a highly complicated diet in the heated Artemia. 



