OF WASHINGTON, VOLUME XV, 1913. 47 



season. Histological work on the photogenic organs of these 

 primitive forms may be of much value in the problem of photo- 

 biogenesis. 



One night last fall (October 18, 1912) the writer went to a spring 

 in the woods on the Virginia shore of the Potomac opposite 

 Plummer's Island, and noticed a faint point of light on the wet 

 surface of a rock, which was at first mistaken for a young glow 

 worm. A pocket electric flashlamp was held close to the luminous 

 point and then lighted, revealing a small common-looking Collem- 

 bolan. Thinking a mistake in location had been made the light 

 was put out and when the eyes were again adjusted to the dark- 

 ness the luminous point was located exactly by placing a finger 

 on each side and the electric light again flashed on, corroborating 

 the first observation. The live specimen was then gotten into a 

 clean vial and examined with a hand-lens in the dark and also 

 by artificial light. No local light organs were to be seen, the 

 light being constant and general but not intense enough for one 

 to see the legs or antennse. The possibility of its being a case 

 of infection by luminous fungal or bacterial growth was considered 

 but as the specimen remained alive and luminous for three nights 

 this hypothesis seems improbable. More specimens were sought 

 immediately and in moving a leaf a very short dim flash attracted 

 attention. When the light was thrown on the place a minute 

 (about 1 mm. in length) white Collembolan of another genus was 

 found but as it was not seen to flash again it was not taken, the 

 impression of the flash being thought to have been an optical 

 illusion similar to "seeing stars." When, however, ten minutes 

 later the same impression of a very short, weak flash was again 

 caught and traced to the same kind of minute white Collembolan 

 which, happily, flashed a second and a third time while under 

 examination, it became evident that the flash was net subjective 

 but objective. Further search that night was without success. 

 Although the two little creatures, alive in a moist vial, were 

 looked at frequently no light was again seen from the small one. 

 The next evening more specimens were sought, but only two, one 

 of each kind, were found. These acted as on the previous evening 

 but the larger was crushed and lost in trying to get it into a vial. 

 The smaller one was only seen to flash twice. Colder weather, 

 and the increasing light from the moon made several more attempts 

 to find material fruitless. 



The specimens were sent to Prof. J. W. Folsom who kindly 

 determined the larger form as a species of Anurida hitherto un- 

 reported from this country which may prove to be one of the 

 European species, while the smaller form agrees fairly well with 

 Neanura quadrioculata Guthrie. 



