198 ANIMAL BEHAVIOUR 



big brain type is relatively poor in ingrained capacities of 

 instinctive behaviour but is eminently educable: the chick 

 reared in an incubator in the laboratory does not recognise 

 what water is, even when it is thirsty and standing in it; 

 it does not know what its unseen mother's cluck means ; and 

 it will stuff its crop once or twice with worms of red worsted. 

 But it learns to find its way about with prodigious rapidity. 

 The little brain type is rich in ingrained capacities of in- 

 stinctive behaviour, but is relatively non-educable. If a bell- 

 jar be placed over the nest of a ground-wasp, from the 

 door of which the inmates are wont to fly away, they are 

 psychically unable to force a path out amid the herbage 

 pressed down by the edge of the glass. Even when those 

 outside force a way in, they cannot come out again, or give 

 their fellows a hint how to escape. 



It must not be supposed, however, that the little brain type 

 is unable to profit by experience. We know in fact that they 

 build up complex chains of associations. It is instructive 

 to recall Professor Yung's experiments with hive-bees. Of 

 20 taken in a box into the country 6 kilometres from 

 Geneva, 17 returned; of those 17 taken next day out on 

 to the lake, none returned. This is to be contrasted with 

 the successful return of the terns which were taken from 

 Bird Key in the Tortugas to Cape Hatteras, 850 miles into 

 seas never before visited; yet some returned in safety to 

 their nests. 



Those who incline to use in reference to ants and bees, 

 crabs and spiders, the terms we need in describing our own 

 activities, should remember the great differences in the plan 

 of the nervous system in the respective ranks of Arthropods 

 and Vertebrates. In the former there is much less centralisa- 

 tion; the cerebral ganglia are connected with a ventral chain 



