192 



K. S. LASHLEY 



coefficients of correlation obtained in this way are given in 

 table 16. Only one of these, that of Clone D' is more than twice 

 its probable error, and this one is negative. The others are all 

 too small to have any significance. The large negative corre- 

 lation of Clone D' is the result of the inclusion of a single parent 

 (the stem parent of the clone) which produced a large number 

 of progeny with few tentacles and was thus heavily weighted in 

 the computation of the coefficient. 



The Clones A— {AlA) and D contain such large numbers both 

 of parents and offspring that it is almost certain that the low 

 correlation is not the result of chance, but truly expresses an 

 almost total absence of similar variations in parent and progeny 

 within the clone. In so far as the coefficient of correlation is a 

 reliable test of heredity we may conclude that there is no inherit- 

 ance of variations in the initial number of tentacles of Hydra 

 viridis. 



For Clone D the fraternal and grandparental correlations were 

 likewise computed; they are given in table 17. Like the parental 

 correlation, the grandparental is too small to have significance. 



TABLE 16 



Correlation of the initial number of tentacles of parents and progeny ivithin the clone 



TABLE 17 

 Ancestral correlations, clone D 



Parental 



Grandparental 

 Fraternal 



0.0038±0.018 



-0.0495±0.018 



0.0770±0.006 



NO. OF PARENTS 



251 



68 



no. of progeny 

 (pairs) 



1395 



1307 



10766 



