BEHAVIOR OF VERTEBRATES 451 



and a 2 cm. circle. Another series of experiments, however, 

 showed that the crows were reacting not to absolute size but 

 to relative, i. e. to the larger circle. They also learned to dis- 

 tinguish a circle from a triangle and from a hexagon under 

 conditions where form was the only constant factor. 



Szymanski's (34) aktograph curve for birds shows a high 

 degree of activity for the morning hours. In the hours imme- 

 diately after noon the activity decreased and then with great 

 constancy rose again just before the beginning of the night 

 rest. In this respect it resembles the waking (day) curve of 

 men given by Helpach. The movements of the birds can be 

 inhibited not entirely but greatly in intensity and also in general 

 nature by darkness. 



SOUND 



Mammals. — There are only three papers to report on auditory 

 sensitivity in connection with vertebrates this year. Shepherd 

 (31) using the method which he had previously employed with 

 raccoons and monkeys investigated sound discrimination in cats. 

 The notes were blown on an ordinary harmonica or sounded 

 on a piano. The animals were to climb up in a cage for food 

 at one note or refrain from climbing when another was sounded. 

 He thinks that he found positive proof of pitch discrimination 

 as well as discrimination of intensity in noise. The constant 

 presence of the experimenter makes possible other clues and 

 renders these results doubtful as Johnson's work with dogs 

 has shown. 



Considering the work mentioned above and other similar 

 studies the following report by Morgulis (23) seems almost 

 incredible yet perhaps our apparatus or methods are at fault. 

 He discusses clearly and concisely the Pawlow method and 

 makes a brief report on Usiewitch's study of the auditory re- 

 actions of the dog by this method. He found an auditory 

 faculty much keener than man's. The dog perceived one-eighth 

 of a tone and tones of a frequency of vibration quite beyond 

 human reach. He found absolute memory for sounds and his 

 dogs could distinguish the shortening of an interval by less than 

 one-fortieth to one-forty- third of a second. 



Hunter (12) has less startling results in a report which he 

 makes upon some studies of the auditory sensitivity of the 

 white rat which are now in progress at the University of Texas. 



