40 ORGANIC BEHAVIOUR 
conclusion that acquired modes of behaviour are not here- 
ditary nowise commits us to the belief that heredity has nothing 
whatever to do with them. Though what is acquired may 
not be transmitted, what one may term the acquisitiveness is 
unquestionably inherited. Though this, that, or the other 
acquired mode of behaviour may have no direct descendants, 
the power of acquiring any one of them under the appropriate 
circumstances is handed on as an invaluable legacy. Just as 
the mirror which has reflected a fleeting scene retains no 
lasting image of the bygone events, so heredity may retain no 
impress of acquired characters; but just as the mirror keeps 
its power of reflecting such scenes, so does heredity transmit 
the power of acquiring such characters. As the leaves of the 
oak are renewed each successive spring, so may acquired modes 
of behaviour be repeated in each successive generation if only 
the requisite conditions recur in due season. 
From what has preceded it may, therefore, be inferred that 
organic behaviour may arise either through modifications 
occurring in the plastic tissues, or through variations having 
their origin in the germinal substance. Broadly speaking, 
however, we may regard as predominantly due to adaptation 
those congenital modes of behaviour and those organic re- 
sponses which on their first occurrence are relatively definite 
in character, and which are directed to a biological end, for 
whose attainment the tissues have had no preparatory training ; 
and we may regard as predominantly due to accommodation 
those responses which are, so to speak, learnt by the tissues in 
the course of individual life. Both are dependent on heredity, 
but in different ways. What the animal owes to heredity may, 
indeed, as I have elsewhere said,* be classified under two 
heads. Under the first will fall those relatively definite modes 
of behaviour which fit the animal to deal at once, on their 
first occurrence, with certain essential or frequently recurring 
conditions of the environment. Under the second head will 
fall the power of dealing with special circumstances as they 
arise in the course of a varied life. The former may be 
* “ Habit and Instiuet,” p. 26. 
