234 History of Luminescence 



position became known as the " Theory of Abyssal Light " and occa- 

 sioned a considerable amount of discussion in books on ecology such 

 as the Animal Life (1881) of Karl Semper (1832-1893) , professor of 

 zoology at the University of Wiirzberg. It was more or less upheld 

 by Wyville Thompson, Alexander Agassiz, and others, and particu- 

 larly supported by C. C. Nutting (1859-1927) , who had previously 

 written on The Color of Deep-sea Animals (1898) and Phospho- 

 rescence in Deep-sea Animals (1899) . Nutting revived the " Theory 

 of Abyssal Light " as late as 1907. While a very high proportion of 

 deep-sea organisms can produce light, the number of these forms is 

 certainly not sufficient to give a general illumination. The purpose 

 of the complicated lanterns of deep-sea Crustacea, squid, and fish can 

 be reasonably assumed to be attraction, recognition, warning, etc., 

 but the use of light by large numbers of organisms, and particularly 

 unicellular forms, merely floating at the surface of the sea, is still 

 problematical. 



Of all naturalists, Charles Darwin (1809-1882) might be expected 

 to devote considerable space to luminous animals. In the Journal of 

 Researches (1839) compiled during the voyage of the " Beagle," 

 Darwin did record observations of luminous animals encountered 

 on his travels, for example a (dead?) cuttlefish, fireflies, and sea 

 phosphorescence near La Plata off the coast of South America. The 

 five years (1831-1836) of world wide travel on the " Beagle," to- 

 gether with observations on the English glowworm, supplied the 

 material for later remarks on luminescence, as Darwin never left 

 England after his return from the voyage in 1836. 



However, the Origin of Species is disappointingly brief in discus- 

 sions of luminous animals. Under the heading " Special Difficulties 

 of the Theory of Natural Selection," there is merely a statement that 

 the evolution of luminous organs is to be placed in the same cate- 

 gory as the evolution of electric organs.^* Darwin apparently had 

 great difficulty in explaining why electric organs appeared to have 

 arisen in diverse groups of fishes and in diverse regions of the body. 

 An even more diverse distribution of luminous organs is found 

 among various luminous animals, and the number of species pos- 

 sessing luminous structures is far greater than those with electric 

 organs. Concerning the latter, Darwin wrote: "It is impossible to 

 conceive by what steps these wondrous organs have been produced." 



The best description of Darwin's views on bioluminescence is 



^^ See pp. 150-151 of the Origin of species, London, John Murray, 1872. This is the 

 sixth edition. In the fourth (1866) , Darwin wrote that evolution of luminous organs 

 offered an exact parallel to electric organs but the statement does not occur in the 

 first edition (1859) or the second (1860) or the third (1861) . 



