318 BIOLOGICAL LECTURES. 



were not hit, would surprise and alarm it, and the impulse to 

 save itself from clanger would naturally take the form deter- 

 mined by the instinct, if the instinct existed. This seems to 

 me more probable than Darwin's suggestion of a mere trick or 

 play. 



d. The Habit Theory Losing Ground. 



The two instincts of pouting and tumbling, claimed as dem- 

 onstrations of the habit theory, thus turn out to be explicable 

 only on the selection theory. It is significant that this theory 

 is fast losing ground even among the psychologists. A. Forel's 

 conversion illustrates the trend of opinion. " I, too," he says, 

 " used to believe that instincts were hereditary habits, but I am 

 now convinced that this is an error, and have adopted Weis- 

 mann's view. It is really impossible to suppose that acquired 

 habits, like piano playing and bicycle riding, for instance (these 

 are certainly acquired), could hand over their mechanism to 

 the germ-plasm of the offspring." l 



In his latest work, Habit and Instinct, Lloyd Morgan has 

 also abandoned the theory. On the same side stand James, 

 Baldwin, Ziehn, Fliigel, and others. The following, from Karl 

 Groos, pp. 60, 61, will show how the difficulties with the theory 

 are multiplying. 



"As regards instinct," says Groos, "there is, further, the 

 a priori argument that it is inconceivable how acquired connec- 

 tions among the brain cells could so affect the inner structure 

 of the reproductive substance as to produce inherited brain 

 tracts in later generations. And, finally, there is this consid- 

 eration mentioned by Ziegler as a suggestion of Meynert's : 

 It is well known that in the higher vertebrates acquired asso- 

 ciations are located in the cortex of the hemispheres. As an 

 acquired act becomes habitual, it may be assumed that the cor- 

 responding combination of nervous elements will become more 

 dense and strong, and the tract proportionally more fixed. This 

 being the case, it follows that the tracts of acquired and habit- 

 ual association, as well as those of acquired movement, pass 



1 Gehirn und Seele, 1894, p. 21. Taken from The Play of Animals, by 

 Groos, p. 56. (Translated by Elizabeth L. Baldwin.) 



