LIGHT BY LIVING ORGANISMS—McDERMOTT. oa 
°° 
marine forms, e. g., the Cephalopoda and the Pennatulide, give lights 
of several colors. Among the insects the only forms known definitely 
to present wide differences from this general similarity are the trop- 
ical species of Phengodes as observed by Barber (*) and others, which 
possess a photogenic organ, located back of the head, that gives a dis- 
tinctly reddish light. No spectroscopic studies of this red light of 
Phengodes have been made. Coblentz (*°) has given spectrographic 
proof of the differences in the color of the lights of Photinus pyralis, 
P. consanguineus, and Photuris pennsylvanica, attention having been 
called to the physiologic differences by the author (‘*) and others, 
[Knab (), Turner (®)]. The author has recently had an opportunity 
to examine the light of Phengodes laticollis (female) with the pocket 
spectroscope referred to in his paper in the Canadian Entomologist, 
1910 (**), and found it to consist mainly of a narrow band in the 
yellow-green and green, with very much fainter ends stretching toward 
the red and blue; the definite ends of the band could not be made out 
on account of the feebleness of the light, and the predominance of 
the greenish band may, of course, be mainly due to the greater 
retinal sensitiveness to these tones. 
Forsyth (7) has claimed that cultures of certain photobacteria give 
spectrophotographic evidence of the existence of ultra-violet rays in 
their emitted light. It seems to the author that this observation is 
in need of confirmation, not that it is impossible, of course, but that 
it is at variance with previous work and with present ideas of the 
properties of physiologic light. McDermott (**) failed to find evi- 
dence of ultra-violet radiation in the light from cultures of Pseudo- 
monas lucifera Molisch, and, as would be expected, also failed to find 
any indication of appreciable radioactivity. 
It need scarcely be said that the light of the firefly affects the pho- 
tographic plate; obviously spectrophotographic studies could not 
otherwise have been made upon it. Photographs have been taken 
by means of the light of the photogenic bacteria and of the cucuyo. 
In 1896 Muraoka (*) announced that he had proved the penetra- 
tion of metal films by means of the light of the firefly in a manner 
similar to that of the X-rays. The author has failed to find any evi- 
dence of the penetration of thin sheet copper, aluminum foil, or the 
black paper with which X-ray plates are wrapped by the light of 
Photinus pyralis. It seems that under certain circumstances sub- 
stances which do not actually emit penetrating radiations may affect 
the photographic plate, and an explanation of Muraoka’s results has 
been offered by Molisch ( ®) based upon bacterial or vapor influ- 
ence; but when we consider that his results were published only a 
little while after the discovery of the X-ray it seems possible that 
Muraoka was just a little over-enthusiastic. However, Singh and 
