S K. S. LASHLEY 



Mean number of 

 tentacles 



Clone A' 6.907±0,026 



Clone D' 5.844=fc0.029 



" Difference (A' - D') 1 .063±0 .039 



0.557 

 0.537 



After two weeks in mass culture the difference between the 

 two clones persisted and was, indeed, increased by 35 per cent. 

 The significance of this increase will be discussed later. 



TABLE 11 

 Variations in clones A' and D' 



Similar results were obtained from populations of the two 

 clones grown in mass culture. The results from five pairs of 

 mass cultures will be considered. 



Two battery jars were filled with pond water; to each a few Elodea 

 stalks free from foreign Hydras were added; and each was inoculated 

 with 50 polyps, the one from Clone A, the other from Clone D. Cyclops 

 were added every week for three weeks. At the end of a month 100 

 polyps were taken froni each culture and the numbers of their ten- 

 tacles were recorded. The variations were distributed as shown in 

 table 12, I. The constants obtained from this are: 



Mean number of 



tentacles a 



Clone A 6 . 56 ± . 056 . 8284 



Clone Z) 5.86±0.033 0.4903 



Difference {A - D) 0.70±0.060 



Five weeks later samples were again taken from these cultures. 

 Their variations are shown in table 12, II. The constants for these 

 groups are : 



Mean number of 



tentacles a 



Clone .4 6.797=fc0.042 0.5038 



Clone D 5. 457 ±0.045 0.5539 



Difference (A - D) 1.340±0.061 



