of biological science, that the discrimination between species and 
non-species (= varieties) must play an important part in all 
research which aims at the explication of the origin of species. It 
is unnecessary to expand on that any further. 
In our researches on the systematics of Lepidoptera we have 
come across some facts which, in being followed up, proved to be 
a striking illustration of the point to which I have just referred. 
There is a remarkable incongruity in the systematics of many not 
nearly related genera of Butterflies which resemble each other, and 
which, without prejudice, we shall call mimetic, as is customary. 
From what we know of the systematics of Heterocera, which 
resemble members of other orders of Insects, e. g. Hymenoptera, 
the principle involved holds good to a great extent also there. 
I shall abstain from entering at any length into the classification 
of the genera represented on the slides. The details may be 
relegated to another place. The tilling of the soil is a very 
important proceeding, but it would hardly be interesting for you 
to assist in the ploughing of the fields, and I propose therefore to 
take vou right away to the harvesting of the modest crop. 
At the outset let us be clear about two points : 
I. Similarities are a reality; they exist. Systematists have over 
and over again been misled by resemblances. The study of resem- 
blance is as much a necessity for the classifier, — who must always 
be on the alert that he is not taken in by what looks alike but is 
different, — as the knowledge of systematics is a necessity for the 
theorist. The similarity remains a reality also in those species which 
resemble each other much more when set out in a cabinet than the 
live individuals at large. 
2. The agreements in aspect and in the details of the structure 
and colour between not closely related species require as much an 
explanation as the differences between nearly allied species. 
Now, from a purely morphological point of view and quite apart 
from the question whether the resemblance serves any object or 
does not, — such as for instance protection, — the similarities may 
be divided into two groups : a) fictitious similarity, and J) genuine 
similarity. 
We will deal with the sham similarity first, asit is an agreement 
with which the systematist as such is not concerned. As examples 
