INHERITANCE IN ASEXUAL REPRODUCTION 201 



the correlation due to the changing clonal mean is too small to 

 account for the parental correlation. No adequate data for a 

 further analysis of the correlation in size is at hand, and it may 

 be that variation in size within the clone is actually inherited 

 but, although conclusive evidence against this is lacking, too 

 much trust should not be placed in the parental correlations. 

 The following points, while based only upon general impres- 

 sions gained dm-ing the experiments and subject to correction 

 by further experimental test, indicate some of the factors which 

 may have been instrumental in producing a high parental cor- 

 relation for size. Size is a character which is modified much 

 more readily and quickly than the number of tentacles by changes 

 in the environment. Hydras, placed in a 0.1 per cent solution of 

 NaCl, in a very few days become dark in color, small, and 

 produce small, dark-colored buds. Similar changes in size follow 

 extreme changes in terxiperature. Upon the restoration of opti- 

 mum conditions the normal size is resumed very quickly. Star- 

 vation is effective in much the same way but to a lesser extent. 

 When a Hydra has been injured slightly, or has passed through 

 a slight depression it grows smaller and produces small buds 

 but eventually both buds and parents resume the normal size 

 of the clone. The size, indeed, seems to be a matter of the 

 immediate state of nutrition of the polyps. Clone A was more 

 readily modified by such agents than was Clone D. This is 

 shown by the following data for the number of tentacles of 

 polyps from mass cultures with and without food for three months: 



3-month mass cultures With food Without food Difference 



Clone A 6.80±0.06 5.52±0.04 1.28±0.07 



Clone D ;..5.52±0.05 5.34±0.03 0.18±0.06 



and by the changes represented in figure 10. Corresponding to 

 this fact, the correlations between the relatives in Clone A are 

 higher than in Clone D, which justifies the suspicion that the 

 correlation between parent and offspring for size within the 

 clone is really due only to the action of the environment. 



