320 THE BIOLOGY OF HYDRA : 1961 



four different temperatures and demonstrated that a temperature 

 shift was not necessary for the initiation of medusa budding. He also 

 observed that the three budding processes exhibited different tem- 

 perature optima. In his experiments, frustule production was maxi- 

 mal at 25°, hydranth budding was maximal at 12° and 20°, and 

 medusa buds were produced only at 28°. 



The work discussed in the present report is concerned with the 

 sequence of budding in developing colonies, some effects of temper- 

 ature and nutrition on the growth and reproduction of polyp col- 

 onies, and certain physiological interactions between the different 

 budding processes. 



METHODS AND MATERIALS 



Polyps of C. sowerbii were collected on glass microscope slides 

 submerged in a limestone quarry pool near Bloomington, Indiana, 

 where populations of the medusae were known to occur regularly 

 (13). Laboratory stocks were established; and for these experi- 

 ments frustules were removed from stock cultures, isolated in Syra- 

 cuse watch glasses, and incubated in an 18.5° (± 1.5°) constant 

 temperature room. Approximately two days later the culture dishes 

 were transferred to shallow glass trays through which charcoal- 

 filtered tap water was continuously passed. In most experiments 

 the shallow glass trays were partially immersed in constant-temper- 

 ature baths. Culture water was provided from a charcoal filtration 

 system manufactured by the Illinois Water Treatment Company, 

 Rockford, Illinois (Model No. CC-24). 



Polyps were fed counted numbers of oligochaete worms {Aeo- 

 losoma hemprichi Ehrenberg) by hand on alternate days or at spe- 

 cified intervals. The worms were cultured on rice-agar plates con- 

 taining a mixture of protozoa and l^acteria as described by Brand- 

 wein (2). 



PATTERNS OF BUDDING 



The basic pattern of development and reproduction of a polyp 

 colony is illustrated in Figure 4. Fifteen frustules were isolated at the 



