THE GENESIS OF LIVING ORGANISMS 233 



basis for parental care, and can be judged only in connection 

 with that. 



All implements of animals that we know as yet, arise 

 through instinctive actions, in which neither memory nor 

 experience play the slightest part. A bird that has grown up 

 in altered conditions and has never known the parental nest, 

 makes one for itself on exactly the same plan as that which 

 governed the nest of its parents. 



It is worth emphasising that every part-action, such as 

 the seizing of the straws which are used to build the nest, is 

 invariably carried out with unfailing sureness ; there is no 

 hesitation or choosing. We do not yet know what are the 

 indications that guide the birds in this. 



Fabre did pioneer experimental work on instinctive actions 

 when he disturbed the burrow of the digger wasp and inter- 

 fered with its care of its young. He showed that, however 

 well the entrance to the burrow be masked, it is confidently re- 

 discovered ; as soon as the burrow is found, the insect feeds 

 its larvae in the prescribed manner. On the other hand, 

 if the upper wall of the burrow has been removed, and the 

 insect is allowed to enter its dwelling, which is no longer 

 shrouded in darkness, the indications are lacking that lead 

 to the feeding of the young, and the wasp gives that up, 

 even if she be treading on her own larvae. 



It also seems that, with bees and wasps, certain indications 

 must appear in a certain order if the rhythmical course of 

 these insects' very complicated instinctive actions is to proceed 

 successfully, whether these have to do with the constructing 

 of the dwelling itself or with the actual care of the young. 



Recently, too, we have had some more exact information 

 about the making of the spider's web. But concerning the 

 co-operation between the rhythmical impulse-sequence con- 

 ditioning the action and the external indications which affect 

 this rhythm, we remain quite in the dark. 



