EVOLUTION OF INSTINCTIVE BEHAVIOUR 107 
certain definite directions independently of their relation to 
the environment. But it is scarcely probable that instinctive 
behaviour is mainly due to any such inherent tendency—of 
the nature of which in any case we know but little. Setting 
this on one side, therefore, we have two hypotheses : first, 
that instincts are the result of natural selection ; secondly, 
that they are due to the inheritance of acquired habits. These 
two views we will now proceed to consider. 
We have seen that Professor Wundt distinguishes two 
classes of instinctive acts : first, those which are acquired or 
have become wholly or partly mechanized in the course of 
individual life ; secondly, those which are connate or have been 
mechanized in the course of generic evolution. ‘The laws of 
practice,” he says,* ‘suffice for the explanation of the acquired 
instincts. The occurrence of connate instincts renders a sub- 
sidiary hypothesis necessary. We must suppose that the 
physical changes which the nervous elements undergo can be 
transmitted from father to son. . . . The assumption of the 
inheritance of acquired dispositions or tendencies is inevitable 
if there is to be any continuity of evolution at all. We may 
be in doubt as to the extent of this inheritance; we cannot 
question the fact itself.” 
Now, the application of the term “instinct,” both to 
acquired and to connate behaviour, seems to prejudge the 
question of their genetic connection. And since we have the 
well-recognized term habits for actions the performance of 
which becomes automatic through frequency of repetition, we 
may substitute this term, or the phrase habitual acts, for the 
‘acquired instincts” of Professor Wundt. Modifying, there- 
fore, his statement in accordance with this usage, the fact 
which, he says, we cannot question is that acquired habits are 
inherited as congenital instincts. ‘This opinion has long been 
held: G. H. Lewes regarded instinctive actions as transmitted 
habits from which the intelligence, through which they were 
originally acquired, had lapsed. Darwin believed that such 
inheritance was a factor in the evolution of instinctive 
* « Lectures on Human and Animal Psychology,” p. 405 
