270 S. O. MAST 



nation produced by means of a pocket electric lamp, a candle 

 or a kerosene lamp. Only in two or three instances was there 

 any indication of orientation and in these exceptional cases 

 the reactions were very indefinite. These results, together with 

 the fact that orientation in the male ordinarily does not begin 

 until after the flash of light which induces it has vanished, 

 demonstrate conclusively that the process of orientation and 

 the direction of locomotion after orientation are not regulated 

 by the continuous action of light, and that these reactions are 

 consequently not in accord with Loeb's theories of tropisms 

 according to which orientation is, as he puts it (1906, p. 135) 

 "a function of the constant intensity." Stimulation which 

 results in orientation in the fire-flies studied is unquestionably 

 due to changes in light intensity much as it is in Stentor, Euglena 

 and many other similar organisms (see Mast, 191 1, pp. 80-205) 

 and the insects remain oriented, not because of continuous 

 action of light in accord with Loeb's theories, but because they 

 tend to take a comparatively straight course in the absence of 

 external stimulation. And since the external stimulating agent 

 does not act continuously in directing this animal on its course 

 after orientation, there can be no a priori necessity for assuming 

 that it does in other animals, as Loeb (191 1, p. 478), Parker 

 (191 2, p. 463) and others appear to hold. 



The responses to flashes of light in both the male and the 

 female fire-flies are unquestionably adaptive and an explana- 

 tion for them must be sought along the same lines as an explana- 

 tion for any other adaptive characteristic in living organisms. 

 It is needless to add that the aim of poetically all scientists in 

 explaining natural phenomena, including the psychic, is to 

 trace the order of events back to a mechanical basis. But we 

 may as well face the facts squarely and realize that with reference 

 to reactions it is questionable whether this has as yet been ac- 

 complished in even a single case. The assumptions of Loeb 

 and Bohn to the contrary notwithstanding. 



SUMMARY 



1. The Western Maryland fire-flies are found in dark crevices 

 or under ground during the day. In the evening, when it is 

 still light enough to read, they come out ; the females climb to 

 the tips of grass or onto other objects and remain quiet; the 



