Characters, Hereditary and Acquired. 91 



subject by briefly stating, and considering, what he 

 has said upon the subject. 



The answer of Weismann to difificulties which arise 

 against the ultra-Darwinian theory in the domain of 

 instinct, is as follows : — 



" The necessity for extreme caution in appealing to the sup- 

 posed hereditary effects of use, is well shown in the case of those 

 numerous instincts which only come into play once in a life-time, 

 and which do not therefore admit of improvement by practice. 

 The queen-bee takes her nuptial flight only once, and yet how 

 many and complex are the instincts and the reflex mechanisms 

 which come into play on that occasion. Again, in many insects 

 the deposition of eggs occurs but once in a life-time, and yet 

 such insects always fulfil the necessary conditions with unfailing 

 accuracy '." 



But in this rejoinder the possibility is forgotten, 

 that although such actions are now performed only 

 once in the individual life-time, originally — i. e. when 

 the instincts were being developed in a remote 

 ancestry — they may have been performed on many 

 frequent and successive occasions during the individual 

 life-time. In all the cases quoted by Weismann, 

 instincts of the kind in question bear independent 

 evidence of high antiquity, by occurring in whole 

 genera (or even families), by being associated with 

 peculiar and often highly evolved structures required 

 for their performance, and so on. Consequently, in 

 these cases ample time has been allowed for subse- 

 quent changes of habit, and of seasonal alterations 

 with respect to propagation — both these things being 

 of frequent and facile occurrence among animals of all 

 kinds, even within periods which fall under actual 

 ' Essays, i. p. 93. 



