December 1, 1916] 



SCIENCE 



785 



same time maintain a rhythm would be a 

 quite different task. 



There are some eases in which animals do 

 act in synchronism with an external rhythm, 

 but so far as I have observed they are always 

 cases in which the time of the animal's actions 

 is regulated by a powerful force from the envi- 

 ronment, and fall under one of the two follow- 

 ing heads: (1) Slow rhythms, such as those 

 of the seasons, or of day and night, in which 

 there are changes in temperature, light, etc., 

 which have plenty of time to act on the organ- 

 ism; (2) cases in which there is bodily con- 

 tact between the organism and that with which 

 it keeps in synchronism, as the case of a canary 

 swinging on a swing-perch, or that of certain 

 spiders swinging on their webs. Are there 

 any cases which do not fall under either of 

 these two heads? Some observers have re- 

 ported them, but let us examine their reports. 



Dr. Edward S. Morse 1 cites a case from 

 memory in which he saw " fireflies flashing in 

 unison," but he gives no exact details. He 

 quotes a paper by Mr. Blair 2 mentioning the 

 same phenomenon; but Mr. Blair states that 

 he never observed the synchronism himself, 

 and he does not cite any authority who has 

 observed it. Dr. Morse in another paper 3 

 quotes R. Shelford as observing a tree full of 

 fireflies pulsating " so that at one moment the 

 tree would be one blaze of light, whilst at an- 

 other the light would he dim and uncertain." 1 

 This last clause makes it appear that some 

 fireflies were not in synchronism with the 

 others, and thus brings in the statistical fal- 

 lacy to be mentioned presently. Dr. Morse 

 quotes Dr. H. C. Bumpus as another observer 

 of the phenomenon; I wrote to Dr. Bumpus, 

 asking certain questions, and he kindly sent me 

 the following statements as to his observation : 

 he saw the synchronism in perhaps 50 fire- 

 flies distributed over two acres; he noticed 

 the synchronism only as he was passing the 



i Morse, E. S., Science, February 4, 1916, 169- 

 170. 



2 Blair, K. G., Nature, December 9, 1915, 414. 



3 Morse, E. S., Science, September 15, 1916, 

 387-388. 



* Italics mine. 



area, so can not say how long it lasted; the 

 interval between flashes was perhaps a half 

 second; he thinks the synchronism was not 

 accidental and not an illusion; but he thinks 

 there were also some fireflies that were flashing 

 asynchronously. 4 ' Now, where a large number 

 of fireflies are flashing at slightly differing 

 rates there must be a great amount of acci- 

 dental synchronism; to determine whether 

 there is a degree of synchronism not due to 

 mere accident, one would need a statistical 

 examination. Viewing any large assortment 

 of instances without statistical methods, one 

 can see in them whatever one is predisposed 

 to see; and we are always predisposed to per- 

 ceive a rhythm — this is a well-known psycho- 

 logical fact. I once had an experience which 

 I think was like that with the fireflies : I was 

 looking at a great area of water covered with 

 ripples flashing in the sunlight, and the flashes 

 I saw were all synchronous, at a rate of per- 

 haps three per second; but their synchronism 

 must have been an illusion. 



Dr. Morse 5 quotes a different case, from 

 Cox, who says : 



Certain ants . . . when alarmed, knock their 

 heads against the leaves and dead sticks . . . every 

 member of the community makes the necessary 

 movement at the same time. 



This case would seem to necessitate that 

 the ants perceive time relations, for each ant 

 must know when the sound is te- come and 

 must anticipate it by making the head move- 

 ment. It is much more probable that the 

 synchronism was an illusion of the observer. 



Professor W. B. Barrows 6 reports seeing a 

 bittern sway gently from side to side as the 

 grass around it was swayed by the wind. But 

 it is doubtful if the observer, seeing the bird 

 against a moving background, could tell truly 

 whether it swayed or not. The details which 

 are given make the phenomenon seem very like 

 an illusion. 



In 1897, Dolbear 7 stated that all the crickets 

 in a given field chirp simultaneously. But 



s Morse, E. S., loc. tit., 387. 



« Barrows, W. B., The Auk, April, 1913, 187- 

 190. 



t Dolbear, A. E., American Naturalist, Vol. 31, 

 970-971. 



