No. 515] BEHAVIOR OF THE DOMESTIC FOWL 675 



cult to see how this second reaction could have been de- 

 veloped as a result of an accidental success, especially 

 when it is borne in mind that the manoeuvre was first ini- 

 tiated and fully perfected within two days of the time 

 when manoeuvre number one was discontinued. Whether 

 manoeuvre number two is a modification of number one, 

 whether it arose from imitation (which is doubtful, since 

 no person or other fowl is known to have performed the 

 action before it was perfected by the cockerel), or whether 

 it is the result of a chance success following random move- 

 ments, the writer is not prepared to state. Notwithstaixl 

 ing the fact that manoeuvre number two is so different 

 from number one, it is perhaps more reasonable to as- 

 sume tentatively the correctness of the first hypothesis. 

 But this does not explain the origin of manoeuvre number 

 one, although it surely demonstrates a very effective modi- 

 fiability in the behavior of the cockerel. In the present 

 instance it is also noteworthy, perhaps, that when the first 

 manoeuvre was prevented by the presence of the sheet of 

 tin, the cockerel did not profit by an imitation of the hens, 

 which continued to work the feeder from behind as in the 

 first case mentioned above. 



Believing that there are certain theoretical considera- 

 tions arising from the foregoing observations which would 

 be of interest to comparative psychologists, the writer 

 has requested Doctor Yerkes to add hereto comments that 

 seem pertinent to the question in hand. The writer would 

 also take this occasion to express his thanks to Mr. Roy H. 

 Waite, Assistant in Biology, for preparing the photo- 

 graph which accompanies this paper; also to Mr. Holden, 

 of the College poultry plant, for some of the data here 

 presented. 



COMMENT UPON DR. HADLEY'S OBSERVATIONS 

 Neither casual observation nor systematic experimentation with the 

 domestic fowl has furnished many instances of the type of behavior 

 described by Dr. Hadley. Consequently his observations have considerable 



