Raymond Pearl 
255 
made but give the same results. Also, though usually more than one coefficient 
of correlation for random pairing will be given it has not been thought necessary 
to publish but one random correlation table for each series. We have then in 
Table XVI. the coefficients measuring the correlation between the lengths of the 
two members of random pairs of conjugants. It will be understood that when 
two values are given for a single series, these values represent different trials. 
No two random tables on the same material will, of course, give identical results. 
I have tried to give examples of the better and worse results which one gets. 
TABLE XVI. 
Length-Length Correlation in Random Pairs of Gonjugant Paramecia. 
Series 
Characters 
Coefficient of 
Correlation 
Table 
A 
Length 
of X 
Length of Y 
- -0847 + -0462 
A 
A' 
Y 
- -1075 + -0460 
A 11 
C 
•>i 
A' 
r 
•0449 + -0474 
Cll 
AA 
i) 
X 
Y 
■0345 + -0337 
)? 
X 
Y 
-•0360 + -0337 
It is at once evident that actual conjugation and random pairing of conjugants 
are quite different things. No one of these random values can be regarded as 
significantly different from zero, whereas for the same characters and the same 
individuals paired together as they are in actual conjugation, the coefficients are 
> "5. The results given for Series A are the most divergent from zero of any 
of the lot, and in the second of these trials we have a result which may just 
possibly be significant in comparison with its probable error, but certainly the 
others are not. We do not even find agreement as to the sign of the random 
correlation. It would seem that some other factor besides mere random pairing 
among the conjugants is necessary to produce the high degree of correlation which 
we find in conjugation. 
To test this matter still further I made random pairings in the same way for 
(a) non-conjugants and (6) pairs, one member of which was a conjugant and the 
other a non-conjugant, and also (c) I considered as a pair the two non-conjugants 
which happened to lie in the field of the microscope nearest to each pair of 
conjugants measured. 
These pairings were made to meet special objections which might be raised 
against considering what we are dealing with here as real homogamy. First it 
might be said that the observed correlations were in some way due to the fact 
that conjugants are differentiated from non-conjugants, and that random pairs of 
non-conjugants might show a spurious homogamic correlation. Random pairings 
(a) and (6) should test any such hypothesis as this. Again it might be maintained 
that since at different points in the culture and at different times the environment 
no doubt differs slightly, there would be a corresponding local differentiation of 
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