ABILITY OF ANIMALS TO KEEP TIME WITH RHYTHM 447 



flock, each goose flaps its wings at its own rate, and thus is free 

 to increase or decrease its speed; even so, the military precision 

 with which geese form in line when moving at high speed through 

 a fluid medium is a remarkable accomplishment. If pelicans 

 can maintain a still closer line while at the same time each 

 pelican beats its wings never faster and never slower than the 

 leader, this is a most astonishing feat, more skillful, probably, 

 than any synchronous rhythmic locomotor activity of human 

 beings. If Wheeler is correct, his observations should certainly 

 be verified and the phenomenon studied in detail by means of 

 photographs and cinematograph films showing flocks of pelicans 

 in flight. 



Wheeler (10) suggests that animals exhibit " a kind of ' Ein- 

 fiihlung,' " but this term is surely inappropriate. He mentions 

 also " a fine sense of rhythm." But it has not yet been proved 

 that animals below man can clearly perceive a rhythm. An 

 ex-cavalry officer writes to me that he regularly observed during 

 parade that the moment the band began to play all the horses 

 at once adjusted their step and forthwith kept perfect time 

 with the music. If this observation were correct it would seem 

 to show that each horse was clearly aware of the rhythm of his 

 own step, of the rhythm of the music, and of the relation between 

 the two. But probably the observation was not correct. On 

 the other hand, if it can be proved that two animals come grad- 

 ually into synchronous rhythmic activity and continue in per- 

 fect synchronism, as Shull 3 reports, with some reservation, for 

 crickets, and Wheeler for pelicans, this does not prove that the 

 animals perceive rhythm as such. The least assumption would 

 seem to be that each cricket has two tendencies: each must 

 have, first, a tendency to chirp in approximately a certain 

 rhythm, the rate of which is not greatly different in different in- 

 dividuals; and this tendency of each animal to its own rhythm 

 must be sufficiently plastic to yield to the second, which is 

 an innate reflex tendency to chirp on receiving the auditory 

 stimulus from the chirp of another cricket. But even this much 

 has not yet been proved beyond question. 4 



3 Op. cit. 



* Since this review went to press the following additional note has appeared. 

 Gates, F. C. Synchronism in the Flashing of Fireflies. Science, N. S., 1917, 

 46, 314. This writer arrives at the conclusion that "complete synchronism in the 

 flashing of a group of fireflies is simply a very rare accident." 



