228 A STUDY IN HEREDITY 



parental care is continued. Furthermore, it is developed to a 

 very great extent only among such animals as not only tend their 

 young for prolonged periods, but also lead gregarious lives. When 

 animals, after laying their eggs, abandon them to chance, it is 

 clear in cases where mind {i.e. consciousness and all that results 

 from consciousness) plays a part in securing survival that such 

 mind must be considerably developed from the moment of hatch- 

 ing. Hence it is that in such animals instinct greatly pre. 

 dominates. Moreover, they cannot acquire traits by imitation 

 from their parents, and, therefore, whatever is acquired by the 

 one generation is completely lost to the next; in other words, 

 they have no traditional knowledge, and all that is mental in the 

 individual is either inborn or has been discovered by himself. 

 But when the animal, after birth, is protected for a prolonged period 

 by its parent, it is clear that instinct (inborn knowledge and ways 

 of thinking and acting) becomes less necessary for survival, since 

 an opportunity is afforded of acquiring fit knowledge and ways of 

 thinking and acting from the environment, particularly from the 

 parent. It is then possible for knowledge to become traditional, 

 and to be handed down from parent to offspring. When, in 

 addition, such animals lead gregarious existences, the individual 

 has the opportunity of acquiring mental characters, not only from 

 the parent, but from other members of the community as well, 

 and then complex mental acquirements have the best chance of 

 being transmitted, instead of being lost. Under such circum- 

 stances the power of acquiring useful mental characters becomes 

 a main factor in the struggle for existence, and those individuals 

 who most possess it survive in the greatest numbers, and, there- 

 fore, concurrently with the growth of knowledge, occurs an 

 evolution of the power of acquiring knowledge and a correspond- 

 ing retrogression of instinct, which, in the ancestor, was a main 

 factor of survival, but is now no longer so 



I have given the dragon-fly as an example of an active animal 

 which does not tend its young, and in which, therefore, instinct is 

 developed to a high degree. The ant, on the other hand, is an 

 animal which not only tends its young, but also lives in great 



