20 The Developmental Characters of
species, we thus arrive at a more certain indication of the
true affinities, i.e., the blood relationships, than by com-
paring adult individuals only.
In order to show the application of these principles, I may
perhaps be permitted to give a hypothetical case. Suppose,
for example, that the foals of the horse were frequently or
invariably striped when young, but lost their stripes as they
grew towards maturity. We should be justified on this
ground alone in believing, with a great amount of proba-
bility, that the horse had descended from a striped ancestor,
and if the foals of an allied species, such as the ass, were
also striped when young, this probability would be greatly
increased. If, on extending our comparisons, we found that
other allied species, such as the zebra, were striped through-
out their lives, we should conclude, in accordance with the
principles of the descent theory, that the horse and ass were
derived with the zebra from a common ancestor having the
characters of the latter species, and since the horse and ass
have, so to speak, outgrown the striped stage of their
existence, which, on our supposition, is retained only during
a short period of their younger stages of growth, we should
say that these species were farther advanced in development
i.e., were phyletically younger than the zebra.
From the above considerations, it will be seen that the
ontogenetic development may thus throw much light on the
past history of a species or group, and through this on the
true systematic affinities. I may now pass on to our imme-
diate subject.
The two systems of classification now made use of by our
Lepidopterists are those adopted in Stainton's 'Manual of
Butterflies and Moths' (1857), and by Doubleday in his
'Synonymic List' (1866). In the former, the Nocturna are
placed between the Bombycina and the Geometrina; in the
latter, the Geometrae follow the Nocturni (Sphinges and
Bombyces of Linnaeus), and are in their turn followed by the
Noctuae, with which they are connected by the Drepanulae
and Pseudo-Bombyces. It is here quite unnecessary to
enter into the histories of these two systems of classification.