CHARLES F. LYTLE 325 



TABLE 1 



Age of polyp coionies at the appearance of the first medusa bud at various 



temperatures. 



hydranth budding at 19-23'^ is associated with a significant delay in 

 the appearance of medusa buds. It also appears that medusa bud- 

 ding may in turn limit frustule production since in all cases the 

 appearance of medusa buds is preceded by a decline in the produc- 

 tion of frustules. 



Further evidence for this interaction between medusa budding 

 and frustule budding has been provided by McClary ( 14 ) . He ob- 

 served no medusa budding in colonies reared at 12°, 20°, and 25°. 

 In each of these groups there was an irregular but progressive in- 

 crease in the rate of frustule budding for 102 days. His 28 colonies 

 exhibited a rise and subsequent decline in the production of 

 frustules, with the decline corresponding to a maximum in medusa 

 budding. 



To study further interactions between hydranth budding, frus- 

 tule budding, and medusa budding, we have investigated the effect 

 of increased and decreased nutrition on polyp colonies in several 

 ways. In the previous experiments described, frustules for the estab- 

 lishment of experimental colonies were taken from stock cultures 



