456 JOHN B. WATSON AND K. S. LASHLEY 



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strain were hatched under hens. These ducklings were found 

 to be quite tame from the first and as easy to manage and rear 

 as the common duck. Their instincts, however, especially those 

 of feeding, differed widely from those of the common duck. On 

 the other hand, the young of back crosses between the common 

 tame mallards and pure wild black ducks (Anas tristis) gave 

 other results. One such cross gave young which showed three- 

 quarters A. tristis, while in two other crosses the young were 

 only one-fourth A. tristis. The three-quarter A. tristis showed 

 exceeding wildness. They w T ere hard to manage and were 

 reared with difficulty, but their dispositions changed with age 

 and they became much more like ordinary ducks. 



Mammals. Slonaker (23) undertakes to give some expression 

 of the normal activity of the albino rat from birth to death. 

 In studying normal activity at different ages he used a cylin- 

 drical cage which revolved upon a stationary axle. On the axle 

 were fastened the nest box, the food box, and the drinking pan. 

 , These parts were arranged in such a way that the animal had 

 to step to the floor of the revolving cage in order- to pass from 

 the food or water receptacle and vice versa., The weight of the 

 animal caused the cage to revolve whenever he stepped upon 

 the inner surface of the cage. A recording device was installed 

 which indicated the number of revolutions made by the cage 

 and their temporal distribution. Eight young rats were kept 

 with the mother until twenty-eight days of age. Four were 

 placed in the apparatus described above, where they remained 

 constantly, except for weighing and cleaning of the cages, etc., 

 until death. A separate revolving cage was provided for each 

 animal. The other four rats were used as controls. They were 

 placed in separate stationary living cages of the ordinary variety. 

 Several important results are claimed for this research. The 

 daily activity increases rapidly during the first third of the 

 life period, after which there is a gradual decrease until death. 

 During the period of youth and that of old age, the active 

 moments are well distributed over the whole twenty-four hours, 

 whereas, during the prime of life, activity is confined princi- 

 pally to night and rest to day. The rats are thus nocturnal. 

 In regard to the amount of work done, it was found that three- 

 fourths of the total amount done was done before middle age 

 was reached. During the last thirty per cent, of life, only one- 



