US THE EVOLUTION OF INSTINCT 



The Lamarckian theory of the origin of instinct has in 

 more or less modified forms enjoyed a wide popularity among 

 writers on genetic psychology. The veteran psychologist 

 Wundt in his discussion of theories of instinct in his Human 

 and Animal Psychology assumes unquestioningly the trans- 

 mission of acquired characters, practically ignoring the 

 doctrine of natural selection, and even representing that 

 Darwin "explains instinct as inherited habit"! 



One of the most extreme positions is that of Eimer who 

 rejects the theory of natural selection and adopts the pure 

 Lamarckian standpoint. One of his arguments in favor of 

 this theory is drawn from the instincts of the mason wasp, 

 Odynerus parietum. This species provisions its nest with 

 larvae which it paralyzes by stinging them in the ventral 

 ganglia. After collecting several larvae and storing them 

 in a hole in the ground, the wasp lays an egg on the store of 

 food, seals up the hole with clay, and then begins the con- 

 struction of another nest. " What a wonderful contrivance " ! 

 exclaims Eimer, "What calculation on the part of the animal 

 must have been necessary to discover it ! The larvae of the 

 wasp require animal food. Dead food enclosed in the cell 

 would soon putrefy; living active animals would disturb the 

 egg, and accordingly the wasp paralyzes grubs and packs 

 them like sacks of meal one after another in the cell. How 

 did she arrive at this habit? At the beginning she prob- 

 ably killed larvae by stinging them anywhere and then 

 placed them in the cell. The bad results of this showed 

 themselves; the larvae putrefied before they could serve 

 as food for the larval wasps. In the meantime the mother- 

 wasp discovered that those larvae which she had stung in 

 particular parts of the body were motionless but still alive, 

 and then she concluded that larvae stung in this particular 

 way could be kept for a longer time unchanged as living 



