LIGHT BY LIVING ORGANISMS—McDERMOTT. 859 
blentz (ante) photographed the spectrum of the fluorescent light from 
solutions of luciferesceine and of the emitted light of the fire-fly 
itself, and showed that the spectra are almost complementary, and 
that the fluorescent spectrum does not appear on the plates of the 
emitted light of the insect, although these plates were sensitive to 
the wave-lengths embraced in the fluorescent spectrum. In any event 
the intensity of the fluorescence of the material in a single insect would 
be too slight to have any appreciable effect in modifying the color of 
the emitted light. (See Coblentz (**) ). In fact it seems probable 
from the work of Tappeiner and Iodlbauer (*) that if the substance 
should actually fluoresce in the bodies of the insects, it would kill 
them. Pigments and other substances showing fluorescence are not 
unecmmon in animals; Stiibel () has claimed that all animal! 
tissues exhibit fluorescence when exposed to ultraviolet light, while 
Arndt (private communication) states that he has observed the 
presence in most insects of substances which are fluorescent under 
the influence of the X-rays. 
Personally, the writer is inclined to regard the fluorescence simply 
as an incidental property dependent on the structure of some com- 
pound frequently met with in insects of this nature, much as Jordan 
(°2) regards the fluorescent pigment of Bacillus fluorescens liquefaciens. 
Dr. Coblentz finds that these fluorescent extracts exert a strong + 
rotation on polarized light. 
5. BIOLOGIC RELATIONS OF THE PHENOMENA. 
There has been a good deal of discussion as to the significance of 
the photogenic functions for the forms possessing it. There are 
four recent papers of considerable importance in this connection. 
Galloway (”) [Galloway and Welch (%)] has observed the use of 
‘“»hosphorescence”’ as a mating adaptation in an Odontosyllid, Odonto- 
syllis Enopla Verrill, this apparently being the first instance in which 
the relation between this function and the reproductive life of the 
organism has been definitely established. McDermott (*') has con- 
firmed the old and frequently over-looked observation of Osten- 
Sacken (**) that the photogenic function plays an important part in 
the mating of Photinus pyralis, and has extended the observation to 
a few other species of Lampyridae. Mast (#) has confirmed this 
result as applied to Photinus ardens, and brought out the bearing of 
the phenomenon on the problems of phototaxis and orientation. 
Lund (#) #) has made observations on Odontosyllids, Lampyrids, 
and Elaterids, which tend to support the observations recorded in 
the above-mentioned papers. An extended study of the relation of 
the photogenic function to the reproductive life of a large number of 
species of Lampyridae of different genera would be of great interest, 
especially as the females of a great many of the species of this family 
