BEHAVIOR OF VERTEBRATES 421 



do not, but the pupil-valence is the same for the two — green 

 is the strongest color. For the bright adapted human eye the 

 order was G, YB, O, R, BR, B, GB. In the change from bright- 

 ness to darkness the colors O, R, and BR became darker than 

 the GB and B (Purkinje's phenomenon). The results for the 

 bright adapted eyes of the owls were exactly the same as for 

 man, therefore owl's eyes do undergo adaptation in such condi- 

 tions and also show the Purkinje phenomenon. Changes in 

 strength of light, a series of 16, showed that in owls there was a 

 real increase in pupil-motor excitability in dark adaptation, 

 inasmuch as the absolute threshhold of the stimulus lay much 

 lower. The human eye under such conditions showed a sen- 

 sitivity not much greater than in the owl. The results of this 

 investigation agree with those of Hess who showed that cones 

 under daylight vision function similarly to the rods. The dark 

 adaptation experiments showed that the difference between rod 

 seeing and cone seeing is not so great as has previously been 

 supposed. 



Leplat (34), in a histological study of the eyes of birds, in- 

 cluding nocturnal birds, confirms and corroborates the con- 

 clusions of Hess as to their power of accommodation. 



AUDITION 



Mammals. Part I of Johnson's monograph (29) is concerned 

 with the discrimination of pitch in dogs. He gives a critical 

 historical account of the Pawlow method and of the work of 

 Goltz, Merk, Kalischer, Rothman and Swift. The purpose of 

 Johnson's experiments was to try to confirm Kalischer's results 

 under stricter control and to find a method of testing the power 

 of pitch discrimination in higher vertebrates. In the prelimi- 

 nary experiments, two dogs seemed to have perfected a discrim- 

 ination between two tones c(256dv) and g(384dv) when sounded 

 on a tuning fork struck by hand, when sounded on the Stern 

 variator, when sounded on forks and different variators indif- 

 ferently and when included in chords. In response to the low 

 tone, the dogs put their forefeet on a chair and waited to be 

 fed; to the higher tone they were trained to mount a low box 

 for the feeding. It was felt, however, that the control had not 

 been sufficient, that the animals might have been reacting to 

 unconscious cues on the part of the experimenter, who was 



