=] 
: 
D.—ZOOLOGY 89 
definite one, passing through a clearly defined trajectory, admitting of 
little deviation from normality ; it takes place generally in an external en- 
vironment which must be normal for the species, and asa rule the internal 
environment also is kept constant round a particular norm. The activities 
whereby the needs of the organism are satisfied and a normal relation to 
the external and the internal environment is maintained, may be called 
the maintenance activities of the organism, and they underlie and support 
the other master-functions of development and reproduction. 
Our general definition or concept of organism is then an organised 
unity showing the activities of maintenance, development and repro- 
duction, bound up in one continuous life-cycle. A static concept is 
inadequate ; time must enter into the definition ; the organism is essen- 
_ tially a spatio-temporal process, a ‘ dynamic pattern in time,’ as Coghill 
aptly calls it. 
Now all these activities are, objectively considered, directed towards 
an end, which is the completion of the normal life-cycle. One is tempted 
to use the word ‘ purposive’ in description of these activities, but this term 
is used in many senses and has a strong psychological flavour about it, so 
I shall use instead the neutral word directive, which I borrow from 
_Myers.* It is quite immaterial from our simple objective point of view 
whether these directive activities, or any of them, are consciously pur- 
posive. The directiveness of vital processes is shown equally well in the 
development of the embryo as in our own conscious behaviour. 
It is this directive activity shown by individual organisms that dis- 
tinguishes living things from inanimate objects. ‘The peculiar character 
of this directiveness, its orientation towards a cyclical progression of 
organisation and activity, clearly distinguishes it from the static directed- 
ness of a machine, constructed for a definite purpose. It should be noted 
too that the living thing shows a certain measure of adaptability in com- 
pleting its life-cycle, so that the end is more constant than the way of 
attaining it. 
Now from this point of view, which is, I maintain, strictly objective, 
behaviour is simply one form of the general directive activity of the 
organism ; it is that part of it which is concerned with the relations of 
the organism to its external world. Plants show behaviour in this general 
sense just as much as animals do, but they, being for the most 
part sessile and stationary creatures, respond to the exigencies of environ- 
ment, and satisfy their basic needs, mainly by processes of growth and 
differentiation, and only exceptionally by active movements. Thus the 
dune plant seeking water grows an enormously long root which burrows 
down through the sand till moisture is reached. Animals on the other 
hand respond to environment and satisfy their needs by means of move- 
ments, either of the body as a whole or of certain organs. But sessile 
animals, like plants, may also respond or show behaviour by means of 
morphogenetic activity. The hydroid Antennularia, for example, if 
“CC. S. Myers, The Absurdity of any Mind-Body Relation. L. T. Hobhouse 
Memorial Lecture, Oxford and London, 1932. 
