300 
GENETICS: K. S. LASHLEY 
No. of Parents No. of Of spring Coefficient of Correlation 
251 1395 0.0038 ±0.018 
78 439 -0.0342 ± 0.032 
164 859 0.0011 ± 0.023 
28 204 0.0314 =1=0.047 
18 153 -0.2420 =^0.051 
51 154 -0.0750 ± 0.054 
As is well known, the number of tentacles of Hydra changes during the 
life of the individual. When the number of tentacles of each bud is 
compared with the number born by the parent at the time when the 
bud was produced there is a slight correlation in the variations of par- 
ents and offspring. For the first clone recorded above this is 0.096 ^ 
0.016. There is also a sKght positive correlation in the variations of 
the buds produced by a single parent, as is shown by the following : 
No. of Fraternal Coefficient 
Pairings of Correlation 
12099 0.161 ±0.004 
10766 0.077 =1=0.006 
A study of the relation of variations in the number of tentacles to 
environmental changes shows that unfavorable conditions tend to re- 
duce, or to prevent increase in, the number of tentacles of parents and 
at the same time lead to a reduction in the number of tentacles of the 
offspring of these parents. Thus, wherever diversities of environment 
occur in cultures of Hydra there should be produced a likeness between 
parent and offspring that is not the result of heredity. To test this, 
the period of cultivation of the two clones giving the above fraternal 
correlations was divided arbitrarily into five-day periods and the buds 
produced within each of these periods were compared. From this 
comparison it appears that unrelated buds produced under like condi- 
tions of cultivation resemble each other as much as do the offspring from 
a single parent. The coef&cients of correlation between the unrelated 
buds produced at the same time were : 
No. of Coefficiont 
Pairings of Correlation 
95141 0.0774 ± 0.0015 
101872 0.1313 ± 0.0014 
It thus appears that the slight resemblance found between parent and 
offspring and between members of the same fraternity within the clone 
may be due either to an inheritance of variations or to the like action 
of environment upon individuals produced at nearly the same time. 
Statistical methods do not sufEce to distinguish between the two possi- 
bilities. 
