THE 
NEW PHYTOIiOGIST. 
Vol. VIII., No. 7. 
July 31ST, 1909. 
RECENT ADVANCES IN THE STUDY OF HEREDITY. 
(A Course of Lectures, for the University of London, delivered in the 
Summer Term, 1909). 
By A. D. Darbishire. 
LECTURE III. 
The Mendelian Hypothesis. 
N OW we pass from the bright daylight of demonstrable fact 
into the dark and dangerous alleys of inference. It may be 
objected that my metaphor is ill-chosen, inasmuch as, in this instance 
as in most others, the inferences drawn from the facts are not 
merely as clear as, but more illuminating than, the facts themselves. 
My answer to this is that the seeming brightness of the region of 
hypothesis is precisely the danger I wish to guard against. It is 
just because the alleys of inference do not seem dark that they 
are so dangerous. We are too apt to forget that there is no other 
light in them than that shed by our own imaginations ; in other words 
that the order, which we believe we have detected in one of nature’s 
workings, is the product of our own imaginations and is projected 
by us into them, to be subsequently “discovered” as we fondly 
imagine, as a new “ law.” 
Let us therefore during this lecture keep vividly before our 
minds the fact that we are in the region of hypothesis and that in 
order to reduce our deceit of ourselves to as low a minimum as 
possible, we must maintain an attitude of continual distrust of 
ourselves whilst in that region. Our self-deceit can be reduced by 
making it a practice to infer only a very short distance ahead of the 
facts; to refrain from proceeding to further inferences until the 
last one has been established by experiment and observation ; and 
