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ovipositors of the tiny Pteromali ; while in attempting to breed 
caterpillars taken in the field, the chance is so greatly against the 
evolution of a butterfly that hymenopterists actually choose this 
method of supplying their cabinets. ‘Of two hundred larvae of 
Pieris Brassicae] Mr. Drewson, of Denmark, writes to me, £ I ob 
tained only twenty pupae ; all the rest were attacked by Microgaster 
glovieratus, and my own attempts with the larvae of Pyrameis 
Atalanta, both in America and Europe, have been even more 
unavailing. These caterpillars seem to be peripatetic banquetting 
halls of Microgasters and Tachinae.”—(Nature. vol. Hi., ft. 147.) 
Weismann says :— 
“It is clear that in such animals as insects we can only speak 
figuratively of normal death, if we mean by this an end which is 
not due to accident. In these animals an accidental death is 
the rule; and is therefore, strictly speaking, normal.”—{Essays 
upon Heredity, p. 22.) 
A sphere in which accidental death is normal can 
scarcely be regarded as the most favourable for the illus 
tration of the action of Natural Selection, for two reasons : 
in the first place, because there will be little certainty as 
to the survival of favourable variations ; and secondly, 
because in some cases there might be a danger of exter 
minating a group by selection applied after so great an 
amount of accidental death. On this latter point Mr. J. 
Jenner Weir says :— 
“ It appears to me rather that as so few specimens become 
imagines in proportion to the eggs produced, the more need is 
there that these few should survive.”—(Nature. vol. Hi., ft. /66.) 
We may regard the difficulty of “accidental” death from 
another point of view. The analogy of transmutation by 
Artificial Selection, or, in other words, by the isolation of 
similar variants from among the variations necessarily con 
nected with reproduction, teaches us that there must be 
one object to be attained, and one process of selection 
strictly dominated by that object. Therefore, if Natural 
Selection is to work in nature, there must be one risk, one