180 



K. S. LASHLEY 



Mean number of 



tentacles a 



Clone A 5.519±0.035 0.5325 



Clone D 5.346±0.033 0.4970 



Difference (A - B) 0.173±0.048 



The second character studied in these clones was the size of 

 the polyps when about one week old. The measurements in- 

 clude 184 individuals of Clone A and 182 of Clone D. The 



TABLE 13 

 Distribution of variations in the size of clones A and D 



distribution of the variations is shown in table 13. The mean 

 sizes of the two clones are: 



Mean size a 



cu. mm. cu. mm. 



Clone A 0.869±0.021 0.4288 



Clone D 0.322±0.022 0.1504 



Difference {A - D) 0.547±0.023 



The mean age at the time of measurement for members of 

 the two clones was: 



Clone A 7.1 days Clone D 7.8 days 



The difference in size is even more pronounced than the differ- 

 ence in the number of tentacles : individuals from Clone A were, 

 on the average, more than twice as large as those from Clone D.^ 

 The difference in the appearance of the polyps is shown in figure 4. 

 The numbers measured are relatively small but they extend 



' An attempt was made to determine whether the difference in size was due tC 

 a difference in the size of the individual cells, in accordance with the theory of 

 the relation between cell and body size advanced by Popoff ('08). Because of 

 the great mobility of Hydra, accurate measurements could be obtained only for 

 the mature nematocysts. In this character the two clones were identical and if 

 it furnishes an index to the size of other cells the difference between the clones 

 was due to a difference in the number and not the size of the body cells. 



