SECTIONAL TRANSACTIONS.--J, K. 381 
(partial) drives show independent variation with respect to structure, in- 
tensity and object. To regard ‘ drives’—even constituent drives (Partial- 
Triebe)—as determined units of motivation is fallacious. 
Since structure, intensity and object of any ‘ drive’ vary, they must be 
analysed separately. In the case of the retrieving drive, analysis shows that 
its structure can only be defined in very general terms, implying foresight 
and insight. The intensity of the drive varies widely and without clear 
correlation with structure ; it can be measured: because there appears to 
exist a functional relationship between intensity and the range of ‘ objects’ 
towards which the drive is directed. Mother rats, impelled by a strong 
retrieving drive, will carry to the nest, kittens, chicks, ducklings, young 
rabbits, etc., but they may refuse rats smaller but older than the rabbits 
they accept. The decisive property of the ‘ object ’ seems to be its age. 
The maternal drives awaken, as a rule, towards the end of pregnancy or 
after parturition. An analysis of the physiological mechanisms involved 
shows that the ovaries are not directly, if at all, involved. But the anterior 
lobe of the pituitary appears to be engaged in the induction of maternal 
behaviour ; many virgin rats exhibit maternal behaviour after having been 
treated with anterior lobe extracts. 
Prof. D. Katz.— Some problems of the psychology of needs (3.0). 
The study of needs seems to be one of the most important tasks of modern 
psychology. One should first try to obtain a general view of the whole 
range of needs (vital, social, artistic, religious, etc.). When we have got 
this, two other tasks remain to be undertaken. The objects which serve 
the satisfaction of needs must be pointed out and the methods by which 
needs are satisfied must be investigated. The different needs all reveal the 
same fundamental laws. No other need offers, from the point of view of 
content and method, such a profitable object of investigation as the satis- 
faction of hunger. In dealing with the satisfaction of hunger we can show 
some of the fundamental laws of needs. The laws of satisfaction of hunger 
reveal the dynamic relations of all needs, how they are influenced by inner 
and outer factors, and by historical factors which to some extent are rational 
and to some other extent irrational. The concept of need may in some 
fields be more helpful than the concept of instinct, particularly in such 
cases where we meet an amazing plasticity in the adaptation of the behaviour 
to unusual conditions. 
SECTION K.—BOTANY. 
Thursday, September 6. 
PRESIDENTIAL ApprEss by Prof. A. W. Bortuwick, O.B.E., on Some 
aspects of forest biology (10.0). (See p. 195.) 
Mr. J. Ramssottom, O.B.E.—Fungi and forestry (11.0). 
Mr. J. BrYAN.—The preservation and preparation of timbers for industrial 
purposes (12.0). 
The importance of a thorough knowledge of the behaviour of wood in 
order to utilise it to the best advantage is stressed. 
