DOES HYBRIDISATION INCREASE FLUCTUATING VARIABILITY ? 107 
were carried out with self-fertilismg sweet peas.) In reality there is 
no trace of indication as to diminution of variability in the course of 
generations by cultivation in pure lines. There is also no suggestion as 
to any successive formation of new “ fixed’’ types: the given types 
have been present from the beginning—they were found and isolated, 
and the fluctuations about them have not in the least been diminished. 
How should such marvellous effects of cultivation in pure lines be 
possible? The self-fertilismg plants remain self-fertilisers, whether 
they are cultivated in numbered places or without numbers. ‘To control 
this I have made a special research as to the variability in succeeding 
years—of course there is no alteration, the standard deviation, skewness, 
and so on, are the same for the same pure line year after year, oscillating 
to and fro, as all such measures may do. 
Hence there is no talk about diminishing variability in pure lines. 
But should not intercrossing augment variability? We all know that 
hybridisation gives augmented variability in so far as, by intercrossing of 
individuals producing different gametes, the different “ traits ’’ enter into 
new combinations, and soon. But this truism is not in question here. 
Here we have to find out whether intercrossing augments the range of 
fluctuation or not. Intercrossing of individuals belonging to the same 
pure line should hardly give any result of interest—and there is no criterion 
for the success of such an intercrossing experiment, the gametes being of 
the same nature. But it might a priori be probable—in this respect 
I can agree with Plate—that intercrossing of individuals belonging to 
different pure lines would augment the fluctuation in respect of such 
quantitatively estimated characters which (at least in the first generation 
of hybrids) blend in hybridisation. Where we have dominant and recessive 
traits the question is quite different. 
For the study of the problem here in question we must first possess 
well-characterised pure lines, the types and the variability of which have 
been measured and controlled for several generations. I have chosen 
four such pure lines for my hybridisation experiments. Three of these 
pure lines were brown beans (Phaseolus vulgaris, ‘ Princess beans ’). 
Line E: seeds broad and rather large (petals pure white and yellow). 
Line MM: seeds narrow and rather long (petals with trace of purple). 
Line BB: seeds broad and small (petals with trace of reddish-purple). 
The fourth was black (dark-blue) beans (Phaseolus vulgaris; Belgian 
haricot vert hdtif). 
Line SE: seeds very narrow and long (petals purple). 
The dimensions and weight of the beans, being the subjects of the 
research, willbe mentioned more concisely below. Other differences between 
the four lines will not here be mentioned. The black beans were chosen 
because the conspicuous difference in colour made it easy to ascertain 
whether the intercrossing was accomplished or not. 4A priori it was to 
be expected that all the hybrids here in question would show the same 
general behaviour as to the dimensions of the seeds (length, L, breadth, B, 
and breadth-index, J=100B : L). Hence the beh&viour of the guaranteed 
