EIGHT BY LIVING ORGANISMS McDERMOTT. 359 



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 ( 5a ) ). In fact it seems probable 

 from the work of Tappeiner and Iodlbauer ( 64 ) 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 

 uncommon in animals ; Stiibel ( 63 ) 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 

 (32a) regards the fluorescent pigment of Bacillus Jiuorescens 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 ( 22 ) [Galloway and Welch ( 23 )] has observed the use of 

 ' 'phosphorescence " 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 ( 51 ) has con- 

 firmed the old and frequently over-looked observation of Osten- 

 Sacken ( 56 ) that the photogenic function plays an important part in 

 the mating of Plwtinus pyralis, and has extended the observation to 

 a few other species of Lampjoidae. Mast ( 45a ) has confirmed this 

 result as applied to Plwtinus ardens, and brought out the bearing of 

 the phenomenon on the problems of phototaxis and orientation. 

 Lund ( 41 > 42 ) 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 



