D.—ZOOLOGY 93 
with complete disregard for the distinctive characteristics of such 
systems. 
From our organismal point of view, the study of behaviour is neither 
comparative physiology nor comparative psychology ; it is the study of 
the directive activity of the organism as a whole, in so far as that activity 
has reference to the organism’s own perceptual world. It must start 
_ with what Lloyd Morgan calls the ‘ plain tale ’ of behaviour, the full and 
accurate description of what organisms do, and of what they are capable. 
Though plants also show behaviour in this general sense, and their whole- 
response to environment is a proper subject for study, it will lighten our 
discussion if we limit it to the behaviour of animals. 
The plain tale description of animal behaviour must begin with a study 
of the natural history and ecology of the animal. Most animals are 
restricted to one definite and rather specialised kind of environment ; 
they are adapted both in structure and activity to inhabit some particular 
ecological norm or ecological niche. We must discover by field observa- 
tion how the animal finds this ecological niche to begin with, and how it 
maintains itself therein. We must investigate how it counters changes in 
its environment, how it defends itself against enemies, how it finds or 
captures its food. All this is straight natural history in the old sense, 
the study of the ‘ habits ’ of animals, and it is linked up closely with the 
modern study of ecology. It is the necessary basis for the more detailed 
study of behaviour. It is also the clue to much of the behaviour shown 
in the artificial conditions of a laboratory experiment.® 
Clearly then we must start with direct observation of the animal’s 
behaviour in the field, or in experimental conditions that approximate as 
nearly as possible to the normal. We must then ask what is the animal 
trying to do, what is the objective end or aim of its action? Sometimes 
the animal is doing nothing in particular ; it is resting or merely waiting 
for something to turn up. Usually, however, the animal is active, is 
showing behaviour ; its actions are directed to some end, are aimed at 
satisfying some need, and we can determine by observation and experi- 
ment what that end is ; the sign that the end is attained is the cessation 
of the train of action. ‘Thus, to take a very simple example, if you remove 
a caddis larva from its tube, by the simple method of prodding it gently 
from behind with the head of a pin, it will move restlessly about until it 
finds the empty tube. Then it will enter the mouth of the tube head 
first, creep through, and perhaps widen the narrow hind opening of the 
tube, but it will finally turn right round inside the tube so that its head 
comes out at the front end, and it is then able to get about normally. 
The aim of the train of behaviour is attained—normal relations to en- 
vironment are restored. If you have removed the tube so that the larva 
cannot find it, it will achieve its end by another means, provided the 
materials are available, for it will then construct a new tube. ‘That is 
an example of simple directive behaviour, and it also illustrates the general 
tule that the end is more constant than the method of reaching it. 
6 E.S. Russell, The Behaviour of Animals, London, 1934. 
