ix ANIMAL BEHAVIOUR 173 



in the individual by structural changes in the nervous 



/ o 



system, but it is not known to what extent, if indeed 

 any, the results of individual habituation can be entailed 

 upon the offspring. The theory once widely held that 

 instinctive predispositions to go through a certain routine 

 are the hereditary results of lapsed intelligence is no 

 longer in favour, mainly because of the difficulty of be- 

 lieving in the hereditary transmission of individually 

 acquired characters. None the less, it may be said, it 

 seems to be part of the strategy of Animate Nature to 

 economise mental activity for higher issues by a struc- 

 tural organisation or registration (badly called mechanisa- 

 tion) of capacities for effective behaviour. It is probable 

 that the steps in the hereditary organisation of be- 

 haviour are due to germinal variations (" inborn in- 

 spirations," some one has said) and not to the entailment 

 of individual learning. 



It is interesting to find that particular tropisms peri- 

 odically repeated sometimes take such a grip of the 

 individual constitution that they are exhibited even in 

 the absence of the liberating external stimulus. Thus 

 the little green worms called Convolutas, well known on 

 some flat beaches, as at Roscoff in Brittany, come up 

 out of the sand when the tide goes down, and retire into 

 the sand when the tide comes up ; and Bohn has demon- 

 strated that they will go on doing this for a couple of 

 weeks in a tideless aquarium away from the sea, or even 

 in a test-tube with some sand. Similarly, some hermit- 

 crabs which are in the way of making for the light at 

 high tide and away from the light at low tide, will con- 

 tinue to do this for some days in a tideless aquarium. 

 Periodic activities often repeated seem to take a grip of 

 the body, becoming in some way enregistered. 



11. Rational Conduct. In the case of man, and prob- 

 ably in his case alone, there is sometimes evidence of 

 rational conduct as contrasted with intelligent be- 

 haviour. We cannot describe such conduct without 

 using general terms ; it involves experimenting with 

 ideas, conceptual as distinguished from perceptual in- 

 ference ; it is controlled in reference to an ideal or a 



