1878.] The Senses of the Lower Animals. 315 
in faCt, are merely instances of warnings furnished by 
sensuous perceptions more acute than our own. We pro- 
nounce it a mystery that the swift should leave us by mid- 
August, when, according to our feelings, we are in the height 
of summer. But could we see and feel with the swift we 
might perceive a change amply sufficient to prompt mi- 
gration. 
Even the attraction of a virgin female moth for the males 
of her species, as already described, has been referred to 
the convenient class of “ instincts.” It must be a curious 
instinCt, indeed, which will aCt to the windward and not to 
the leeward. We never think of saying that the hound 
pursues the fox by instinCt. If unwilling to concede to him 
the possession of reason, we may say that it is by instinCt 
he knows that the odour he detects upon the grass or the 
soil has been left there by an animal which he may over- 
take if he follows up the trail. But the aCt of recognising 
this odour we ascribe simply to one of his senses. Why 
take another course as concerns the Satnrnici Carpini ? If 
an animal detects the presence of any objeCt at a distance, 
it can only be effected by one of two methods ; either mate- 
rial molecules, solid or gaseous, are given off by the objeCt, 
and brought by atmospheric (or aqueous) currents into con- 
tact with the sense organs of the observer, or else certain 
vibrations or undulations, sonorous, luminouSj &c., reach 
him through the medium of the atmosphere 'or the ether. 
Surely neither of these processes can be described as 
“ instinCt,” and he who by implication admits the possibility 
of a third way should at least give us some hint concerning 
its nature and mode of action. 
Here, therefore, is a point of departure for animal psy- 
chology which has not received a due share of attention. 
We must study the senses of the lower animals both struc- 
turally and functionally, more especially in the Articulata, 
where the departure from the human type of organisation 
is so complete, and where the manifestations of intelligence 
are so complex and so nearly rival our own. 
