DEFINITION OF INSTINCTIVE BEHAVIOUR 69 
experience, in which there is, on the subjective side, so far as 
we can judge, no conception of the biological end to be attained. 
What can the animal in the early stages of intelligence know 
of biological ends? Mr. Marshall’s subjective criterion applies 
just as much to a wide range of intelligent behaviour as it does 
to instinctive actions. 
In accepting, therefore, Spence’s statement that when animals 
behave instinctively they perform, without a knowledge of the 
end in view, certain actions tending to their own well-being 
and the preservation of the species, we must take it in con- 
nection with the preceding limitation, remembering that they 
are also performed without instruction and experience. 
A further point for very brief consideration is suggested by 
the phrase in which Spence says that animals are all alike im- 
pelled to the performance of certain actions. As it stands it 
is too sweeping and general. Still, wedo require some explicit 
statement of the facts which he had in mind when he wrote 
the words “all alike.” And we find it with sufficient exactness 
in Dr. Peckham’s definition, where he comprises under the 
category of instinctive behaviour “ all complex acts which are 
performed previous to experience, and in @ similar manner by 
all members of the same sex and race.’ This places congenital 
behaviour in line with morphological structure as a subject for 
comparative treatment. 
One more question remains. What shall we understand 
by ‘“‘complex acts”? In the first place, it is well to restrict 
the term instinctive to co-ordinated actions ; and this implies 
the presence of nerve-centres by which the co-ordination is 
effected. We thus exclude the organic behaviour of plants, 
since there is no evidence in the vegetable kingdom of 
co-ordinating centres. In the second place, the co-ordination 
is, as we have seen, congenital, and not acquired in the course 
of individual experience. Young water-birds, and indeed 
young chicks, as soon as they are born, and have recovered 
from the shock of birth, can swim with definite co-ordination 
of leg movements. Here the definiteness is not only congenital, 
but connate, if we use the latter term for an instinctive activity 
