342 



THE BIOLOGY OF HYDRA : 1961 



consistent results, an exceptional record it might be said in a field 

 where over a score of operational factors have been shown to affect 

 the results. In this experiment, ten male Hydra littoralis were 

 grown in 15 ml. beakers in BVC solution^ that had been aerated 

 with oxygen in duplicate vessels 1 and 2, while vessels 3 to 8 re- 

 ceived increasing amounts of BVC solution that had been equili- 

 brated with oxygen containing 10'/ CO. gas. In all cases the Hydra 

 were fed daily with an excess of brine shrimp and then rinsed and 

 placed in clean BVC solution half an hour later when they had fed 

 to repletion. In addition, each vessel was rinsed a second time about 

 five hours later to remove any excreted material present at that 

 time, the pCO^ being readjusted each time the water was changed. 



TABLE 1 

 Control of sexual differentiation in Hydra by pCO^ (From ref. 16) 



1 See p. 338. 



