454 
The Progress of the 
[October, 
and a preservation of the rest with as little reference to any 
properties they possess as if the momentous question had 
been decided by lot. 
From the egg we pass to the larva. Here there are un- 
doubtedly greater individual differences. We can well 
admit that one caterpillar may have keener senses to per- 
ceive the approach of danger, greater agility in escaping, 
more cunning in concealment, an odour less attractive to 
enemies than have others, and may thus derive an advan- 
tage over them in the struggle for existence, and may thus 
fairly be pronounced more fitted for the conditions under 
which it must exist, and better adapted to survive. But 
here also a vast number of cases must occur in which 
chance alone can decide. The totally accidental matter of 
position at some momentous time may be of far greater 
consequence for the life of a larva than a slight variation 
in any of the points just enumerated. Thus an ichneumon 
may oviposit in the bodies of caterpillars a , b, c, &c., whilst 
caterpillar a; may escape from the simple fadt that the 
enemy’s stock of eggs ready to be deposited was exhausted 
before she reached it. Or two larvae upon two different 
plants may each be threatened by the approach of an 
ichneumon. But the one invader may become entangled in 
the web of a spider or be snapped up by a bird, whilst the 
other meets with no hindrance and effedts her purpose. 
In the pupa state, again, no small portion of the deaths 
take place ; and here we have a reversion almost to the 
conditions of the egg. Without any reference to attributes 
of their own; some pupse may have been discovered by 
birds, by field-mice, by hedgehogs, and by other of the 
numerous birds, beasts, or insedts who consume such prey 
with readiness, whilst others by pure accident may have 
escaped. Whatever effedt the first small steps of variation 
may have had in determining the survival of any given 
individual, it seems insignificant compared with the effedts 
of chance. The condition of a Lepidopterous insedt, from 
the egg to its emergence as imago, seems very much like 
that of the inmates of a town under the inflidtion of a 
heavy bombardment. It may perish or it may survive, 
neither alternative being so much determined by its own 
peculiar attributes as by the position which it occupies at 
some given moment. With the mature butterfty the case is 
different. We can well conceive that variations in point of 
speed, not relatively greater than such as are well known 
to occur between individuals of one species, may turn the 
scale for life or for death, and can thus imagine the gradual 
