nOMOTYPOfSLS IN THE VEGETABLE KINGDOM. 
355 
seen the mean of the index-correlations for musliroom gills and ivy leaves = ‘4108, a 
result by no means bad, or widely divergent from the mean residt of all our data. 
If we test the hypothesis as to the value of the cross-correlation we have the 
following results arranged as in the case of the mushrooms : 
Product of direct homotypic length correlation with organic length- 
breadth correlation = ’48 9 7 
Product of direct homotypic breadth correlation and organic length- 
breadth correlation = -4048 
Product of mean of direct homotypic length and l:)readth correlations 
with the organic length-breadth correlations = '4773 
These numbers have to he compared with the cross length-lu’eadth correlation, i.e., 
with •5157. 
We see that, as in tlie case of the mushroom, they are somewhat too small, 
48 say as compared with 5'2. But the difference is considerably less here, and 
allowing for the action of disturbing factors, I think we may say that the two 
quantities under investigation are at least of the same order of magnitude. There 
I think we must leave the hypothesis until my zoological measurements are 
reduced. 
I give the four tables of classified data for the absolute lengtlis and breadths of 
the ivy leaves. In the first or organic correlation table the reader will he able, in the 
distribution at least of breadths, to find sometliing of the irregularity to which I have 
already referred. 
VI. SUMMAIIY OF PtESCTLTS. 
(23.) In summing up my results and comparing them with those obtained for 
fraternal correlation by my co-woilvers and myself, I felt some difficulty. If I made a 
selection of wliat I considererl the fjest homotypic correlation series, and the best 
fraternal correlation, I might well lay myself open to the charge of selecting statistics 
with a view to the demonstration of a theoretical law laid down beforehand. 
Accordingly, I determined to include all my liomotypic results, except tliose for tlie 
absolute dimensions of musliroom gills and ivy leaves, where it was pretty evident 
that we had to a greater or less degree an influence exerted by the gi-owth factor. 
I thus drew up Table XXXIL, containing a summary of all my residts. I am quite 
sure that heterogeneity due to one or anotlier cause, exerts an influence of one kind 
at the top, and differentiation an influence of another kind at the bottom of this 
table. The amount of these influences and of other disturbing causes, one cannot 
measure and allow for. I can only hope tliat having taken a fairly wide range of 
races and characters, tlie influences tending to obscure the homotypic correlation, on 
tlie one hand by raising it, and on the other liy reducing it, will about balance, and 
2 z 2 
