LITERATURE FOR 1916 ON THE BEHAVIOR OF VERTEBRATES 437 



form of data upon the relative stimulating effect of different 

 wave lengths upon the light and dark adapted eye, the ability 

 of the fowl to react upon the basis of wave lengths, and the 

 appearance of relatively abrupt changes in the stimulating value 

 of different parts of the spectrum." The Yerkes- Watson color 

 apparatus, with slight modifications, was used and the experi- 

 ments were subject to a high degree of control. 



In a study on the spectral sensitivity of birds Watson (28) 

 says that the limit of the chick's spectrum at the red end lies 

 probably between ^ = 7000 and ^=7150; at the violet end, 

 between *• = 3950 and X = 4050. This range is similar to that 

 of man except in the extreme red end. The range of spectral 

 sensitivity in the homing pigeon lies approximately between 

 * = 4200 and X = 7100. 



REFLEX AND RHYTHMIC ACTIVITIES 



General. — The conditioned reflex is urged by Watson (26) as 

 a method par excellence in psychology. He describes the tech- 

 nique and discusses various phases of the problem, persistence, 

 reinforcement, inhibition, etc., and concludes by sketching ways 

 in which the reflex may be used to obtain differential reactions. 

 Craig (6) would like to know whether we find in animals any- 

 thing like the synchronism of rhythm exhibited by men as they 

 march or dance or keep step to music. Such a correlation of 

 activities involves a conceptual awareness of the relation of 

 one's own action to that of others. But, the author asks, 

 may not animals have some innate mechanism which would 

 bring them into synchronism with some external rhythm. He 

 examines the evidence for many forms and says that if we reject 

 (1) the slow rhythm due to day and night or seasonal changes 

 and (2) cases in which there is bodily contact with the other 

 rhythmical object as canary and perch or spider and web the 

 case seems good only for the cricket chirping, " And even in 

 that case it is still somewhat in doubt whether their simultaneity 

 is accidental or due to the influence of environment or due to a 

 lock and key adaptation by which one cricket stimulates the 

 other." 



Mammals. — The reflex by means of which cats in falling always 

 turn in the air and land on their feet was studied experimentally 

 by Muller and Weed (19;. They found that the normal cats 



