LOW INTELLIGENCE OF KEPTILES AND FISHES, 387 
by education, and being performed under the direction of 
an Intelligence much higher than the boasted reasoning 
power of Man. 
485. In the classes of Reptiles and Fishes, the manifesta¬ 
tions of Intelligence are so slight as to be scarcely distin¬ 
guishable. We find them capable of such an amount of 
education as enables them to recognise individuals from whom 
they have been accustomed to receive food ; but they seem to 
have very little further power of profiting by experience ; and 
we do not find that individuals ever shape-out for themselves 
a new course which can be regarded as purely rational. This 
very low grade of Intelligence obviously corresponds with 
the very rudimentary development of the Cerebrum in these 
classes (§§ 453, 454). 
The contrast between Instinct and Intelligence will be more 
fully displayed in a future Chapter; in which also a general 
account will be given of the Mental Operations to which the 
Cerebrum of Man is subservient. 
CHAPTER XL 
ON SENSATION, AND THE ORGANS OP THE SENSES. 
486. All save the very lowest kinds of Animals possess, 
there is good reason to believe, a consciousness of their own 
existence, first derived from a feeling of some of the changes 
taking place within themselves ; and also a greater or less 
amount of sensibility to the condition of external things. 
How far any such endowment can be possessed by creatures 
which are destitute of a nervous system, and which are little 
else than particles of animated jelly, may be questioned. But 
there can be no reasonable doubt that where a nervous 
system exists, whatever consciousness any Animal may pos¬ 
sess of that which is taking place within or around itself, is 
all derived from impressions made upon the extremities of 
certain of its nervous fibres; which, being conveyed by them 
to the central sensorium , are there felt (§ 430). Of the mode 
in which the impression, hitherto a change of a material cha¬ 
racter, is there made to act upon the mind, we are absolutely 
ignorant; we only know the fact. Hence, although we com- 
c c 2 
