346 
PROFESSOR K. PEARSOX AXD OTHERS OX 
It will be seen at once that they are sensibly too small (say, '56 as compared with 
•63). But having recognised the influence of heterogeneity in the growth stages 
of our material, the divergence is, I take it, of a mag’nitude rather to confirm than 
confute the hypothesis as to the relationship of direct and cross homotypic correla¬ 
tions. It must be remembered that we are dealing with average results. Our main 
proj^osition is that heredity is not a factor of life peculiar to sexual reproduction, but 
merely a phase of the larger factor, which we have termed homotyposis, or the 
tendency of the individual to put forth undifferentiated like organs with a certain 
degree of resemblance. Our subsidiary proposition is : that if the direct homotvpic 
correlation oscillates about a certain mean value, and the cross homotypic correlation 
be the product of organic and direct homotypic correlations, then we should expect 
to find the average degree of resemblance of brethren equal to the average degree 
of resemblance of undifterentiated like organs in the individual. 
All then I think we can safely say for the gills of mushrooms is that the relation of 
the direct and cross homotyjjic correlations is by no means such that it condemns 
our hypothesis, or enforces ns to reject onr subsidiary proposition. The difficulty lies in 
finding adult organisms with undifferentiated like organs with two characters in 
sufiicient qnantit}", easily counted or measured, upon which the hypothesis can be tested. 
The investigation of tlie length and breadth of ivy leaves, to which we shall soon turn, 
siifPers to some extent from the same defects as that for the o-iHs of mushrooms. 
Tables XXIII.-XXVI. contain the leno’th-breadth data for the mushrooms. The 
frequency distributions for length and breadth are given in the last row and column 
of Table XXY. above, and exhiljit in their irregidarity something of the hetero¬ 
geneity of growth to which I have referi-ed. Of the two distributions, I consider 
that for the breadth as the more irregular and consequently the less satisfactoiy. It 
is, of course, harder to determine a definite breadth for the gill than a definite 
length, and I should be well content to compare the product of the homotypic length 
correlation and the organic length-breadth correlation, i.e., '6025, with the cross 
homotypic length-breadth correlation, i.e., '6275, as the best basis for our subsidiary 
proposition available from these measurements on mushrooms. 
(22.) 117/(7 Iv}! (Hedera Helix).—This series was originally undertaken by Dr. 
E. Warrex, his object being to measure the degree of resemblance between ivy 
leaves on the same ])lant, using as his character the index, or ratio of length to 
maximum breadth. It was hoped that in this manner, the growth factor might he 
fairly well eliminated. 
The figures (page 348) indicate how the breadth and length were determined hy 
Dr. Warrex in leaves of somewhat different sliape. 
It will 1)e seen that, as in the case of the gill (fi* the nurshroom, the breadth is taken 
as tlie maximum breadth between tangents to the conttuu' parallel to the length, 
and these tangents do not necessarily go through points like o, a. Twenty-five leaves 
were taken from each of 42 plants by Dr. Warrex, in the neighbourhood of Ctmterbury, 
