i8o 



BIOLOGICAL LECTURES. 



type of luminous organ, in which photogenic substance never 

 leaves the body, is illustrated by the more familiar phosphor- 

 escent organisms, such as fireflies (Fig. i), glowworms, Pyro- 

 phoruSy Euphausia, Nyctiphanes (Fig. 2), Phengodes, Scopelus 

 (Fig. 3), etc. 1 



The phosphorescent organism of this group, as a rule, has 

 good control over its luminous organ, and may often be able to 



FIG. i. Photimis consanguineus, right figure, female ; \zit,ma.Ze. Luminous 

 organs are shaded. 



inhibit the exhibition of light for a considerable length of time. 

 The organism may be endowed with a wealth of structures sug- 

 gestively like the luminous organs, yet they may never satisfy 

 the naturalist that they are such if the exhibition of their lumi- 



1 It is impossible to give any adequate idea of the beauty and complexity of 

 the luminous mechanism of this type without the use of a large number of illus- 

 trations. Some ideas in regard to the size and distribution of the luminous organs 

 that obtain in some forms may be gathered from a few figures that accompany the 

 present paper. 



