10 ORGANIC BEHAVIOUR 
Fig. 2, v.; but it just as often brings it again towards the 
drop, especially a large one. It seems to be a matter of 
chance which result follows. But eventually the little crea- 
ture sails off, since each time it comes within the influence 
of the alkaline fluid it jerks back and turns. It appears, 
then, that when it is swimming in a normal solution a faintly 
acid liquid does not much modify its behaviour, but an alka- 
line fluid evokes a reversal of the cilia; and that when it 
is a slightly acid solution, not only does stronger acid cause 
reversal, but normal fluid produces a similar result. A reaction 
of essentially the same kind is in fact called forth by such 
different stimuli as chemical substances, water heated above 
the normal temperature, or cooled considerably below it, and 
fluids which cause changes of internal pressure within the 
substance of the cell. Nor does it matter where the stimulus 
is applied. If it be applied at the hinder end the infusorian 
still jerks backward, though this may drive it into a destructive 
solution and thus cause death. There is, however, some evi- 
dence of different behaviour in some infusorians according as 
the stimulus is here or there. In other words, the behaviour 
is to some extent related to the position of the part stimulated. 
Furthermore, it may be gathered from Dr. Jennings’s ac- 
count that there is nothing to lead us to suppose that such free 
living cells show any indication of what may be regarded as 
the keynote of intelligent behaviour. They do not profit by 
experience. They exhibit organic reactions which may be ac- 
companied by some dim form of consciousness, but which do not 
seem to be under the guidance of such consciousness, if it exist. 
One of the first lessons which the study of animal behaviour, 
in its organic aspect, should impress upon our minds is, that 
living cells may react to stimuli in a manner which we per- 
ceive to be subservient to a biological end, and yet react 
without conscious purpose—that is to say, automatically. The 
living cell assimilates food and absorbs oxygen, it grows and 
subdivides, it elaborates secretions, produces a skeletal frame- 
work or covering, rids itself of waste products, responds to stimuli 
in a definite fashion, moves hither and thither at random, its 
