Bioluminescence 663 



animals must be kept for some time in darkness before full responsiveness is 

 regained. 



Only a single luminous nemertean, Emplectonema kandai, has been de- 

 scribed.^' Photogenic cells, producing light intracellularly, are distributed 

 over the whole worm. A local response to localized tactile stimulation is 

 seen. A generalized response follows stretching of the animal. 



Among the Annelida luminescence is restricted to species of terrestrial 

 oligochaetes and marine p^lvchaetes. Manv earthworms, on irritation, eject a 

 luminous slime. This mav come from the oral or anal opening or from the 

 dorsal pores.^'*- ^'^ TJie polychaete, Chaetopterus, exhibits a striking lumi- 

 nosity, much of the surface becoming luminous whenever the worm is dis- 

 turbed (Fig. 250). The photogenic cells are located in the hvpodcrmis along 

 with mucus cells, both of which secrete their products to the exterior'-' (Fig. 

 251, C). Suggestive of nerve control of light production is the fact that 

 stimulation of the anterior end of the worm results in a wave of light-pro- 

 duction passing posteriorly. In the transparent pelagic Tomopteris the photo- 

 genic organs are specialized nephridial funnels.'"'^ In luminous scale worms 

 the light originates in certain papillae on the dorsal overlapping scales. Stim- 

 ulation of any portion of the body results in a wave of light production 

 passing posteriorly from the point of excitation, but not anteriorly/"' thus 

 indicating rather clearly an influence of a polarized ner\'ous system. 



Luminous species of arthropods are numerous. They are largely crustaceans 

 and insects, rarely myriapods and arachnids. In fact, it is from a luminous 

 ostracod, Cypridina, that we have learned much of the fundamental char- 

 acteristics of the basic photogenic process. The light-producing organ is a 

 large gland located near the mouth.*'"' Two kinds of cells can be seen in the 

 living gland, one containing large yellow granules (luciferin), and the 

 other, small colorless granules (luciferase) (see p. 667 et seq.). The gran- 

 ules are ejected bv muscle contraction, and the luminescence is extracellular. 



In those copepods showing photogenic capacity the source of the active 

 agents which are expelled into the sea water are small groups of greenish 

 secretory cells on various parts of the body. 



Many euphausids and shrimp possess rather highly differentiated organs 

 having a reflecting layer and lens associated with the light-producing cells 

 (Fig. 251, A). These organs are distributed widely over the surface of the 

 body. The numerous organs appear coordinated through the nervous sys- 

 tem inasmuch as the sequence of their activity may, as in Sergestes,''^ for ex- 

 ample, follow an anteroposterior progression. The deep-sea shrimp, Acanthe- 

 phyra purpurea, has, in addition to typical photophores (luminous organs) 

 of the general type just described, glands near the mouth from which lumin- 

 escent substances may be forcefully ejected so as to permit the shrimp to 

 escape from predators in a luminous cloud. '"' 



Among the insects, luminescence is restricted to members of very few 

 orders. A few species of Collemhola ha\'e been described to glow continu- 

 ously, although varying in intensity with the state of excitation of the indi- 

 vidual. ■'•'• •'^ The larvae of the fungus gnat, Ceratoplanus, and of the tipulid 

 fly, BoUtophila,-^- have been described as luminescent, and in the latter species 

 the adults are also. In these latter flies the light appears to be in the malpigh- 

 ian tubules."^ 



