292 THE AMERICAN NATURALIST [Vol.LVI 



group of controls. Since inbreeding was the rule, the 

 closest possible relationship for the tests and controls in 

 the successive generations was secured; they came from 

 a single pair of grandparents or great-grandparents, and 

 were thus raised at the same time, and after the same 

 number of generations of inbreeding. 



Treatment.— 'Hhe treatment of these rats was by means 

 of the inhalation method, now made familiar by the work 

 of Stockard and Pearl. The rats were placed in closed 

 tanks filled with alcohol vapor ; these tanks have been de- 

 scribed in detail elsewhere (MacDowell and Vicari, '21). 

 Beginning at weaning (28 days) the rats to be treated 

 were placed in the tanks for 30 minutes a day for 7 days. 

 After this the duration of the daily treatment was meas- 

 ured by the reactions of the animals; for the next 14 

 days the rats were left daily in the fumes until they were 

 obviously under their influence; subsequently the rats 

 were left each day until they were completely anesthe- 

 tized. This required from three to four hours for the 

 older rats. 



Criteria. — The term treated is used to indicate rats that 

 were placed in the alcohol fumes after birth. The fol- 

 lowing generations are herein reported: (1) the treated 

 rats, (2) the treated offspring, (3) the untreated off- 

 spring, (4) the untreated offspring of (3) (second un- 

 treated generation following one treated generation). 

 For these rats the following types of data are given: 

 the behavior in the maze, as measured by time per trial; 

 behavior in a multiple choice apparatus, measured by 

 the number of correct first choices ; fertility, judged by 

 the size of the litters and the number of litters; body 

 weight, as judged by growth curves based on weekly 

 weighings. 



Maze-Behavior 

 Apparatus and Training. — The maze used in this study 

 was built according to the details given by Watson ( '14) ; 

 namely, a concentric arrangement of five alleys with door- 

 ways and blind alleys so arranged that the true path from 



