LIMITS OF HEREDITARY CONTROL 877 
not already determined that is needed for our calculation. The 
formula used is as follows: 
2 ox? 
1 - 33.5 
Substituting we get: r = (1 — 5 Te = 0.9348. 
We can use this coefficient of correlation as an index of the 
strength of hereditary control and can say concretely that, so 
far as the total number of scutes in the banded region is concerned, 
the individual is predetermined within certain narrow limits, 
or up to 93.48 per cent of complete determination. Beyond that 
point the variations in the number of scutes are due to differ- 
ences in epigenetic factors, whose nature we do not pretend to 
understand. 
No such close correlation as this has been determined for 
any of the ordinary blood relationships. The closest of all blood 
relationships, namely the fraternal, is represented by a correlation 
constant of only 0.4, a fact familiar to all who have read their 
Galton. Even homotypical parts of the same individual are cor- 
related only a little more closely than are brethren, a fact which 
leads Pearson to conclude that the fraternal relation is only a 
special case of homotyposis. In brief there appears to be no other 
inter-individualistic relationship so close as that which we have 
found to exist between the individuals of our sets of quadruplets. 
If we desire to find correlations comparable in closeness with that 
determined in our material, we must seek them among the closest 
of intra-individualistic relationships, such as that existing between 
the antimetrically paired organs of the same individual. As 
an example of such constants we may cite the correlation coeffi- 
cient between the right and the left sides of the carapace of Gel- 
asimus, which is 0.947, or that between the lengths of right and 
left meropodite of the first walking leg of the same species, which 
is 0.918. These constants are obviously of the same grade as 
that determined for the scutes of our quadruplets. From these 
facts we are doubtless justified in concluding that the four indi- 
viduals of each of our sets is morphologically the equivalent of a 
