ROBERT E. EAKIN 4DS 



Chlorohydm viridissima (Non-green): The non-green Chloro- 

 hijdra were obtained by depriving green organisms of light for 

 several weeks. Upon exposure to light, some soon regained their 

 green color but the others, although subsequently grown in the 

 light, have not regained their color after three years. 



Not shown in this table is the growth rate by asexual budding. 

 This can be most easily expressed in the time required for a doub- 

 ling of the number of hydranths in optimally nourished clones. 

 The fastest growing hydra are the Cldoiohydra, both the green 

 and the non-green strains doubling in about 1.3 days. H. oligactis 

 and Strains I, II, and III of H. Uttoralis double in number in 2.0 



TABLE 2 

 Regenerative response of a "typical" and an "atypical" subclone of Strain II 



Age of subclones Tentacle number at 48 hours* 



^'^y^ Typical Atypical 



48 LS 



24 1.2 



53 4.8 



57 1.4 



68 2.0 



12.3 1.6 



151 4.8 



168 2.7 



188 1.6 



"Average of 18 replicates. 



to 2.4 days, but Strain IV is an unusually slower grower, having 

 a doubling time exceeding 6 days. There is no apparent correla- 

 tion between rate of asexual budding and the rate of tentacle 

 regeneration in the different strains. 



A second intrinsic factor influencing regeneration — inherita- 

 ble variations arising within a clone — is illustrated in Table 2. 

 Some of our erratic behavior finally was traced to the "area-of- 

 the-dish" effect, that is, the regenerative response was related to 

 the area of the culture dish from which an organism was taken. 

 In determining the cause of this behavior, l3uds from parents used 

 in tests were subcloned and their subsequent behavior determined. 

 It was found that (a) some of the parent hydra regenerated few- 



