ARE ACQUIRED CHARACTERS HEREDITARY? 473 



ties in their gait and other signs of nystagmus. Moreover, the young 

 of parents rotated to the left showed different effects from those of 

 parents rotated to the right. The condition is said to have been 

 inherited for several generations. Detlefson, however, noted that the 

 whhled rats and their offspring showed frequent pathological sequelae, 

 such as discharges from the ears, and is now inclined to vronder 

 "whether Griffith has not merely presented us with numerous specimens 

 of some vertebral disease." The impUcation is that the disease once 

 started might be passed on to future generations by infection. It is 

 generally understood that Detlefson has been repeating these experi- 

 ments upon the Wistar Institute standard white rats, and that his 

 results are so far negative. 



The most recent flurry in the field resulted from a brief statement 

 from the well-known Russian physiologist Pavlov, which may be best 

 given in his own words: 



"The latest experiments (which are not yet finished) show that the 

 conditioned reflexes, i.e., the highest nervous activity, are inherited. 

 At present some experiments on white mice have been completed. 

 Conditioned reflexes to electric bells are formed, so that the animals 

 are trained to run to their feeding place on the ringing of the bell. The 

 following results have been obtained: 



"The first generation of white mice required 300 lessons. Three 

 hundred times was it necessary to combine the feeding of the mice with 

 the ringing of the bell in order to accustom them to run to the feeding 

 place on hearing the bell ring. The second generation required, for 

 the same result, only 100 lessons. The third generation learned to do 

 it after 30 lessons. The fourth generation required only 10 lessons. 

 The last generation which I saw before leaving Petrograd learned the 

 lesson after 5 repetitions. The sixth generation will be tested after 

 my return. I think it is very probable that after some time a new 

 generation of mice will run to the feeding place on hearing the bell 

 with no previous lesson." 



Until we have had a complete report of the methods used and the 

 exact data resulting from these methods, it may be well to reserve 

 judgment about Pavlov's extraordinary mice. It may be said, however, 

 that several American investigators, using the approved methods of 

 laboratories of comparative psychology, have tried the same or similar 

 experiments with mice as those of Pavlov, and with entirely negative 

 results. 



And thus stands the problem today. It is no more settled than 



