ANIMAL INTELLIGENCE. 17 
” 
ing it to bea“ provision of Nature ’’ that young birds should 
act in this way for the safety of their own health. I have, 
indeed, heard this behaviour on the part of young herons 
described as a deliberately defensive measure. If one climbs 
a tree in a heronry and approaches a nest containing young 
birds, they poke their posteriors over the side and discharge 
a copious and malodorous volley upon the intruder. Such 
action has all the appearance of design; but it is almost cer- 
tainly no more than the natural automatic action of young 
herons undergoing visceral disturbance through fear or ex- 
_ citement. 
That is an example of very simple functional activity un- 
consciously performed; but it can hardly be doubted that 
some of the most complex and delicate performances of 
.animals very far down in the animated scale are unconsciously 
discharged, or at least undertaken under a mandate with 
which they automatically comply. The silkworm once only, 
and at an immature stage of existence, spins an elaborate 
cocoon wihch no amount of practice could improve. The 
evidence of design is not to be mistaken; but who can suspect 
the builder to be also the architect? At a given period of its 
growth the motor nerves of this sluggish larva set in action 
machinery specialised to work up material which has been 
unconsciously stored. The action is wholly independent of 
the creature’s volition. It must spin, whether it would or 
no, and it can exercise no discretion in the style or shape of 
its cocoon. 
In the case of spiders, we have the action of an adult 
creature instead of a larva; yet the process seems to be none 
the less independent of volition. The design is so much more 
ambitious than the silkworm’s, the structure so much more 
beautiful and complex, and so closely in accord with the 
principles of human engineering that one has more difficulty 
in dissociating it from the independent ingenuity and con- 
scious skill of the worker. Yet the common garden spider 
(Epeira diadema) probably acts unconsciously in setting about 
to spin her web. She (for it is only the female that’ spins) 
does not reflect before setting in motion the mechanism which 
she has inherited from a remote ancestry, though she must 
