INHERITANCE IN ASEXUAL REPRODUCTION 195 



These correlations show a resemblance between the buds 

 produced within a limited time as great as that found between 

 the closest relatives, although these buds were no more closely 

 related to each other than to those produced during other five 

 day intervals. This same effect would be visible in the cor- 

 relation between parent and progeny whenever several gener- 

 ations are included in the same correlation table, as is necessary 

 in the case of Hydra. 



Such effects of environmental action seem adequate to account 

 for all the coefficients of correlation given by Hanel's data and 

 for the very slight positive correlations found for the initial 

 number of tentacles in my own clones. The fact that the number 

 of tentacles of successive buds increases with the increase in the 

 number of tentacles of the parent accounts for the slightly larger 

 correlation found between the number of tentacles of the parents 

 and offspring recorded when each bud was produced. Whether 

 the increase in the number of tentacles of the buds is an inherit- 

 ance of the variations taking place in the parent with growth, or 

 is only a temporary effect of the increased vigor of the parent, 

 must be tested by the success or failure of an attempt to modify 

 the character of the race by the continued selection of variates. 



The effects of selection within the clone 



The second method of testing inheritance, that of continued 

 selection of variates, offers a good many practical difficulties in 

 Hydra owing to the sensitiveness of the polyps to environmental 

 changes. A specimen of H. viridis, collected in the late summer 

 of 1914, was used to found a large clone. Its progeny were 

 bred in individual cultures until 85 members of the clone were 

 obtained. These gave a mean of 6.141 ±0.058 with the dis- 

 tribution shown in table 19. From this clonal population 25 

 polyps with seven tentacles and 25 with six or less were selected. 

 Each was kept until it produced a bud varying from the mean 

 in the same direction as itself. This bud was then selected and 

 kept in the same way until it in turn produced a bud varying 

 in the same direction, and this selection was continued for three 



THE JOURNAL OF EXPERIMENTAL ZO8LOGY, VOL. 19, NO. 2 



