( Hi ) 
THE SPECULATIVE METHOD IN ENTOMOLOGY. 
The Association of Chemistry and Biology in researches 
such as those to which I have drawn attention, has suggested 
a comparison between the methods of research in vogue in 
the two great departments of science of which these two 
subjects are respectively typical. All science necessarily 
begins with observation or experiment, i.e., with ascertained 
facts, and it is perhaps unnecessary to assert that no mere 
collection of facts can constitute a science. We begin to be 
scientific when we compare and coordinate our facts with a 
view to arriving at generalisations on which to base hypotheses 
or to make guesses at the principles underlying the facts. 
Having formed the hypothesis we then proceed to test its 
accuracy by seeing how far it enables us to explain or to 
discover new facts, and if it fails to do this to our satisfaction 
we conclude that our guess has been a bad one and requires 
modification or replacing by a better one, i.e., by one more in 
harmony with the facts. I take it that the course of progress 
is the same in so far as these fundamental methods are con- 
cerned in both departments of science, the physical and the 
biological. It is possibly a matter of individual opinion as 
to how large a body of facts should be accumulated before 
we attempt to draw any general conclusions. There can be 
no doubt that the requirements of one branch of science 
cannot be measured by those of another branch to which it 
has no near relationship. But however large the number of 
facts J and however cautious or conservative the worker may 
be, it is an established doctrine taught by the whole history 
of science, that real progress only begins when we go to seek 
for facts armed with at least the suggestion of a principle if 
not with a complete theory based on facts already accumulated 
by observation or experiment. This is the whole difference 
between scientific observation or experiment and mere random 
or haphazard observation. A naturalist of the old school, 
WilHam Swainson, writing in 1834,* speaks of the "obser- 
* Preliminary Discourse on the Study of Natural Science, p. 51. 
