I. LIFE PROCESSES 65 



day and handled gently for a time. They submitted to this 

 handling without much protest until their eyes were opened. 

 After this time they began to bite when held, and they were 

 so frightened and so nervous that the idea of taming them 

 was abandoned. Two young rats of the third generation, a 

 male and female, were taken in charge by an assistant, Miss 

 Ruth Meeser. She succeeded in taming them so that she 

 could handle them at will throughout their lives. They were 

 always very nervous, however, and would not submit to being 

 held by any one who was not a constant worker in the colony. 



Females of the first, and those of subsequent generations, 

 reared their own young. It was necessary to wear gloves 

 when the young of the early generations were removed from 

 the nest for examination. If the young were returned to the 

 mother with human odor clinging to them she frequently 

 killed them at once or refused to care for them. In later 

 generations the females did not show much concern if the 

 nest was disturbed and the young handled with bare hands. 

 When they were returned to her, however, she usually carried 

 them to a corner of the cage and built a new nest. 



As the generations advanced, the rats gradually lost much 

 of their savageness as well as their fear of man. By the fifth 

 generation they were sufficiently tame to remain quietly in 

 the corner of the cage when the door was opened or the cage 

 cleaned. They came to the front of the cage, as do Albinos, 

 when they heard the sound of the truck that brought food 

 and began eating as soon as food was available. Many of 

 them would take bits of food pushed through the wire of the 

 door, if offered by some one to whom they were accustomed. 

 They were, however, always alarmed at the approach of 

 strangers and promptly went in hiding. Evidently they could 

 distinguish between colony workers and strangers through 

 their keen sense of smell. 



It has been the custom, throughout the course of this ex- 

 periment, to place males of one litter with females of another 

 litter when the young are removed from the mother at tin- 

 time of weaning. These rats, therefore, irrNv up toirt-tln-r 



MEMOIR 14 



