E. NEWTON HARVEY 3 



In addition to the genera listed in the table, occasional reports of 

 luminous species are to be found in the literature for the following 

 groups: Ascomycetes (Xijlaria); Phallales (Ileodictyon, Kalchbren- 

 nera); Turbellaria {Monocelis); Polychaeta {Nereis, Pohjopthahnus); 

 Polyzoa {Memhranipora, Flustra, Electra, Acanthodesia*' ) ; Chaetog- 

 natha (Sogitta); Pteropoda (Creseis, Styiola, Clio, Cavolinia); Proso- 

 branchiata (Pterotrochea, Tonna); Octopoda {Cirrothauma, Ele- 

 doneUa); Pycnogonida (Colossendeis); Araneae (Spiders); Isoptera 

 (termites); Lepidoptera (Arctia); Asteroidea (Brisingia); Ascidiacea 

 (Ciona); Chimaerae (Chimaera); Teleostomi {Parehippus, Riwettus, 

 Exocetus, Xenodermichthys, Halosauriis, Bassozetus, Leucicorus, Ma- 

 criirus, Lampr gram mil s, Mixonus, Malthopsis, Ipnops). Nothing is 

 known of the nature of the hght emission and confirmation of lumi- 

 nosity is to be desired. 



The title of this conference, "The luminescence of biological sys- 

 tems," suggests that self-luminous organisms are the principal ones to 

 be considered and that the chemistry of the various luminescent 

 systems should receive first attention. How may the more than 70 

 quite different groups of luminous organisms listed in Table I be 

 arranged on such a basis? It is always difficult to classify a subject, 

 because those familiar with the field may disagree regarding the 

 proper basis for classification, and because of the usual exceptions 

 to every rule. One basis for characterizing luminescent organisms 

 depends on whether the light emission takes place within the cell, 

 intracellular, I, or the luminous substances are secreted to the outside, 

 extracellular, E. The groups belonging in these categories are indicated 

 in Table I, column 2. 



Perhaps a more fundamental grouping, for which there can be httle 

 criticism on biological grounds, is (1) luminous plants and (2) lumi- 

 nous animals. This classification not only reflects the fundamental 

 difference in chemistry in the animal and vegetable worlds, but is 

 also particularly cogent because in the plant kingdom, whose only 

 luminous representatives are bacteria and fungi, f light production is 



' See K. Kato, Do/;t/f5ugafcu Za5si, 59, 9-10, 1950. 



f The chemiluminescence following photosynthetic processes, invisible to 

 the dark adapted eye, which has been described by Strehler (1951) and 

 Strehler and Arnold ( 1951) is in a different category from bioluminescences. 



