V. II. Blackman. 
74 
also noticed that in many cases the hybrids were inclined to revert, 
often very quickly, to their parental characters, but this is in no 
sense a general law. 
The apparent barrenness of the field in general conclusions 
was partly due to the method of work; with one brilliant exception 
to be mentioned later, the hybrids were considered too generally, 
attention was not sufficiently concentrated on certain special 
characters in the parent, and the behaviour of these investigated in the 
hybrids and in later generations; further, the results were not 
usually treated in a statistical manner. It is this absence of 
general scientific results and, as Bateson has pointed out, the 
veering of interest in other directions with the acceptance of the 
Darwinian theories, that have led to the neglect of the study of 
hybridisation of plants. That the subject is of the greatest import¬ 
ance no one can doubt, and already results of no slight value have 
been obtained. It is being more and more clearly recognised that 
if any real insight is to be gained into the laws of heredity and the 
all important question of “ species ” the subject must be attacked 
not only from the systematic and statistical, but also from the 
experimental side. Now the crossing of two plants of different 
characters and the exact study, in all aspects, of the resulting 
hybrids and their descendants is one of the most obvious experi¬ 
mental ways in which light can be thrown, not only upon the way 
in which the characters are inherited, but also on the relation of the 
various characters, the sum of which constitutes what we call a 
species, a variety, etc. 
When De Vries, who had been led to a study of hybrids in 
relation to his theory of Pangenesis (according to which the whole 
character of an organism is built up of different entities), published 
in March, 1900 , a paper entitled “Sur la loi de disjonction des 
hybrides,” in which he laid down general laws for the relation of 
the characters of the hybrid to that of the parent, it seemed that at 
length the study of hybrids was to throw considerable light on the 
wider question of the laws of heredity. In the following month the 
results were more fully stated in a further paper, but there he 
makes the surprising statement that he has discovered that the 
laws he had deduced were not only not new, but had been fully 
stated and even explained in the same way so far back as 1865 by 
Gregor Mendel. This earlier paper was, however, published in a 
somewhat obscure journal and had been generally overlooked until 
it was disinterred by De Vries, and curiously enough also by 
