LAMARCK’S THEORY OF DESCENT 337 
act of intelligence. None of these can indeed freely 
vary its actions; none of them has the power of 
abandoning what we call its zwdustry to adopt any 
other kind. 
‘There is, then, nothing wonderful in the supposed 
industry of the ant- lion (Myrmelcon formica-leo), 
which, having thrown up a hillock of movable sand, 
waits until its booty is thrown down to the bottom 
of its funnel by the showers of sand to become its 
victim; also there is none in the manceuvre of the 
oyster, which, to satisfy all its wants, does nothing but 
open and close its shell. So long as their organiza- 
tion is not changed they will always, both of them, 
do what we see them do, and they will do it neither 
voluntarily nor rationally. 
“This is not the case with the vertebrate animals, 
and it is among them, especially in the birds and 
mammals, that we observe in their actions traces of a 
true zzdustry ; because in difficult cases their intelli- 
gence, in spite of their propensity to habits, can aid 
them in varying their actions. These acts, however, 
are not common, and are only slightly manifested in 
certain races which have exercised them more, as we 
have had frequent occasion to remark.” 
Lamarck then (chapter vi.) examines into the nature 
of the zwz//, which he says is really the principle under- 
lying all the actions of animals. The will, he says, is 
one of the results of thought, the result of a reflux of 
a portion of the nervous fluid towards the parts which 
are to act. 
He compares the brain to a register on which are 
imprinted ideas of all kinds acquired by the individual, 
so that this individual provokes at will an effusion of 
the nervous fluid on this register, and directs it to any 
particular page. The remainder of the second volume 
22 
