3H 



BIOLOGICAL LECTURES. 



there any case where it can be clearly shown that an undoubted 

 instinct arose from inherited habit, or any case in which it can 

 be made clear that the theory adopted for neuter insects can- 

 not possibly hold ? Both questions, it seems to me, must be 

 answered in the negative. 



4. Weak Points in the Habit Theory. — The habit theory has 

 many adherents still, and Darwin himself often found it a con- 

 venient hypothesis. But neither Darwin nor anybody else has 

 o-iven us a crucial test that would stand beside that furnished 

 in neuter insects. The failure to find such a test is certainly 

 not due to any lack of zeal or effort on the part of the advocates 

 of the theory. The tests claimed are numerous enough, but 

 they always fall short of the requirement. The weak points in 

 the theory are : 



1. It starts on a disputed, if not refuted assumption ; namely, 

 that habits wholly new to the individual and the species, having 

 no hereditary basis predisposing to them, may, as the result of 

 exercise frequently repeated, and continued in successive gen- 

 erations, eventually become hereditary instincts. 



2. It appeals to the less typical rather than to the more 

 typical cases ■ — to cases in which the critical points are unde- 

 termined or doubtful, or open to a different interpretation. 



3. Its definition of habit and instinct verges towards a 

 petitio principii. Two or more classes of instincts are set up 

 so as to facilitate a nearer approach to habit, e.g., acquired and 

 connate (Wundt) ; primary and secondary (Romanes). Habit 

 is used indiscriminately for an action originating in some con- 

 genital variation and an action forced upon the individual by 

 special circumstances. A fundamental distinction, on which the 

 validity of the theory must be tested, is thus ignored. 



c. Two Demonstrations of the Habit Theory Claimed 



by Romanes. 



The evidence adduced to show that habit may pass into 

 instinct cannot here be 'examined in detail. Romanes brings 

 forward two cases — the instincts of tumbling and ponting in 

 pigeons — which he declares are alone sufficient to demonstrate 



