The Nineteenth Century 245 



in review 



From the purely biological point of view, the most important 

 discoveries of the nineteenth century may be stated as follows: (1) 

 realization that all light of the sea is due to living organisms, (2) 

 demonstration that the light of flesh and dead fish comes from lumi- 

 nous bacteria, (3) proof that the light of shining wood is of fungal 

 origin and (4) the discovery of life at great depths in the ocean with 

 a very high proportion of luminous species. In addition a con- 

 siderable array of new luminous surface forms was added. These 

 belonged to some fifteen groups in which luminosity had not pre- 

 viously been described. In order of discovery it was established that 

 luminosity occurred in the following groups: ctenophores (Bosc, 

 1800) ; hydroids (Stewart, 1802) ; Pyrosoma (Peron, 1804) ; brittle 

 stars (Viviani, 1805) ; Radiolaria (Tilesius, 1819) ; teleosts (Cocco, 

 1838) ; sharks (Bennett, 1840) ; a fly larva, Ceroplatus (Wahlberg, 

 1849) ; collembolids (Allman, 1851) ; squid (Verany, 1851) ; sipho- 

 nophores (Meyen, 1834) ; Sagitta (Giglioni, 1870) ; Phyllirrhoe 

 (Panceri, 1873) ; Balanoglossus (Panceri, 1875) ; and the fresh-water 

 limpet, Latia (Suter, 1890) . 



In addition, the fine structure of luminous tissues, was fully 

 worked out and the complicated lantern-like structure of some lumi- 

 nous organs established. It was realized that sometimes the light is 

 of intracellular origin and sometimes appears from extracellular 

 secreted material. 



The physiology, biochemistry, and biophysics of light production 

 made great strides during the nineteenth century, keeping pace with 

 the advancing knowledge of other functional activities of animals. 

 Although details of all these investigations will be found in Chap- 

 ter XVI, together with the more purely biological discoveries, the 

 following fundamental ideas may be regarded as nineteenth-century 

 contributions to the study of bioluminescence: (1) Realization of 

 the part played by stimulation in exciting light production, and 

 discovery of the existence of special luminescence-effector nerves, 

 (2) demonstration of inhibition of the bioluminescence of some 

 forms by light, (3) establishment of the basic facts regarding action 

 of drugs, salts, and other chemicals, temperature, etc., on light pro- 

 duction, (4) disproof of the early view that phosphorus played a 

 part in bioluminescence, and demonstration that in some forms the 

 light is a chemiluminescence connected with enzymic oxidation of 

 a definite organic compound, luciferin. 



Some light intensity and heat measurements of " living light " 

 were made, but the continuous recording of rapid flashes of light 



