CHARLES F. LYTLE 



329 



30 - 



25 



20 



I 5 



10 



^ Daily 



Fig. 11. Production of frustules at three different feeding rates (n = the 

 number of hydranths per colony at the time of feeding). Cultures maintained 



at 23 (±:1 ). 



a direct and proportional increase with increased rates of feeding. 

 The production of frustules, however, was affected differentially 

 (Fig. 11). The animals at the two lower feeding rates produced 

 only a few frustules while the animals at the highest rate showed 

 a large increase in the number of frustules produced. Much of the 

 additional food went preferentially into the production of frustules. 

 The effect of these different feeding rates is summarized in Fig- 

 ure 12. At the lowest feeding rate there were few buds of each 

 type produced. At the intermediate feeding rate there was a 240% 

 increase in the production of hydranths over those produced at the 

 lowest rate of feeding and a 60^ increase in the production of me- 

 dusa buds. Only a 5.1% increase was observed in the production 

 of frustules. At the highest rate of feeding there was a further in- 

 crease (211.8%) in the production of hydranth buds over the inter- 



