1885.] 
Poison-Secreters. 
669 
knowledge spieads, just as does that of any new or newly- 
recognised source of danger. Hence it is not unfair to 
conclude that the possession of defensive poisons is a safe- 
guard to the animal or plant in question. That this protec- 
tion is not universally efficacious must be admitted. The 
poisonous nature of the foxglove does not save its leaves 
from being riddled by snails. The faCt that they are satu- 
rated with canthariaine is no safeguard to certain beetles 
against being munched by hedgehogs and gobbled by ducks. 
It we ask the elder naturalists for an explanation of these 
cases, they tell us that the snail is specially adapted to keep 
down the growth of the foxglove, and the hedgehog com- 
missioned to hold the Spanish fly in check. If we turn to 
the advocate of Natural Selection, he will inform us that 
the Spanish fly has developed a poisonous property by which 
it defies its enemies, or, in other words, that it has survived 
in virtue of having developed such property, whilst its 
assailant, the hedgehog, survives (or at least possesses a 
certain advantage) in virtue of having developed an immu- 
nity against this poisonous property. I can scarcely see 
that the latter answer is more satisfactory than the former. 
Both accept the notion of a game of cross-purposes,— of an 
Agency undoing with one hand what it does with the other. 
Neither tells us why one plant or animal should be protected 
rather than others, or, if protected at all, why this objetf: 
should be effected in one case by poisons, and in another by 
a nauseous smell or taste. Do such points depend on mere 
chance ? 
In plants, at least, evil scents and flavours often prove a 
most efficient safeguard. I know of no plant which enjoys 
such complete immunity from slugs, caterpillars, and aphides 
as does the Escholtzia, free from poison, but saturated with 
an intensely bitter principle. 
But I must now turn to the offensive poisons, — those 
which, by one or other means, are introduced into the body 
of some victim against its will. As usual in Nature, there 
are here marks of continuity, — intermediate links, — so that 
we may often stand in doubt to which class a given poison 
is to be referred. 
We read of plants — though more precise knowledge is 
here needed — which can injure by odours emitted, or by the 
dew which drops from their branches during the night. The 
sensational accounts of the upas-tree of Java, and its death- 
valley, are now relegated to the sphere of the mythical. 
But it seems possible that persons of susceptible constitu- 
tions may be injured by sitting, and especially by sleeping, 
