374 Darwinism, Biometry and Some Recent Biology. I. 
It will be at once recognised that the differences here are rather less than many 
of the environmental differences, and there is no security whatever that these 
26 foundation stock Hydra are really represented by differentiated hereditary 
numbers of tentacles. Yet this table as it stands embraces Hanel's proof that 
number of tentacles is an hereditary character in the " pure line." What evidence 
is there that any one of the numbers of tentacles attached to those 26 parents is 
truly constitutional and not environmental ? In every generation that follows 
Hanel selects from each line two or three individuals to be parents of the following 
generation. In selecting a few isolated individuals in each generation, where non- 
hereditary influences are so influential, we may break the effect of heredity at 
each step, and since such influences are equally effective with heredity, the chances 
are that we shall do so once in every two selections. Only by taking large numbers 
of the high and large numbers of the low, would it have been possible to average 
out the effect of environmental changes. When the line is carried through two 
or three selected individuals only, there is no certainty that the non-hereditary 
variations will average out. Of course this statement proceeds on the assumption 
that heredity is small in this case compared with other factors. Table I gives 
TABLE I. 
Number of Tentacles of Stem Parent and 
Number of Tentacles of Stem Parent, 
nng. 
6 
8 
9 1 10 
11 
12 
Totals 
1 
1 
6 
8 
9 
10 
11 
24 
70 
23 
4 
81 
139 
44 
4 
54 
136 
23 
4 
25 
75 
50 
14 
1 
1 
12 
36 
22 
8 
2 
1 
8 
1 
6 
3 
2 
8 
14 
1 
199 
472 
247 
59 
11 
1 
Totals 
122 
268 
310 166 
80 
19 
25 
990 
Hanel's data for the 26 original parents and their immediate offspring* 
statistical constants obtained aref : 
Parents (26) Offspring (990) Correlation Eegression 
Mean 6-996 7-201 f -230 -138 
Standard Deviation 1-435 -862 1+-011 +-013 
Th( 
* A protest must here be raised against the manner in which this author's data are tabled. No proper 
description is given of the tables, and it is quite impossible to pick out the pedigree of any individual 
beyond the parent. Further, instead of the frequencies of offspring with each number of tentacles being 
given, the total number of offspring is stated and the percentages with each number of tentacles. A 
laborious process had therefore to be undertaken to replace Hanel percentages by the original frequencies. 
It was then found that many of this author's percentages must be wrongly calculated, for their totals 
came to 111, 93, etc., instead of 100, while in other cases it was impossible to determine where one 
or more individuals should be placed on the basis of the percentages given. It is impossible to make 
anything of a return in which 13 individuals are said to occur in percentages of 15, 31, 40 and 8 ! On 
this account 21 families had to be dropped, out of 245 for which data are provided. 
t 1 have to thank most heartily Miss Ethel M. Elderton for the whole of the arithmetical reductions 
of Hanel's data. 
