Animal Luminescence 567 



In addition to the large medusae, many marine naturalists ob- 

 served the smaller transparent hydromedusae but in most cases it is 

 almost impossible to identify the luminous species. Linne included 

 a " medusa noctu vagatur " in the tenth edition of Systema Naturae 



(1758) and Thomas Pennant described luminous Medusa simplex 

 in his British Zoology in 1777. Additional eighteenth-century records 

 of luminescence are due to P. Forskal ^^ (1775) on a trip to Egypt 

 in 1762; to J. Banks "'' and D. C. Solander on Captain Cook's voyage 

 of the " Endeavor " in 1768-1771; to the Dutch naturalist, M. Slabber 



(1771), and to Andrew Sparmann -" (1772), a Swedish physician 

 who thought large luminous spots in the surface of the sea near the 

 Cape of Good Hope were luminous medusae, although he had no 

 real proof. Olaf Schwarz-'^ (1789, 1792) and Adolph Modeer (1792) , 

 both on sea voyages, also saw luminous medusae. Modeer noticed 

 that when the jellyfish was broken up in sea water, the light came 

 from " little sparks " that spread from the medusa like stars. This is 

 characteristic of luminous jellyfish slime, which contains granules 

 whose dissolution is accompanied with a burst of light. 



The scientific study of luminous medusae begins with experi- 

 ments of the Abbe Lazaro Spallanzani, made at Messina during a 

 journey to Sicily in 1788. Spallanzani (1794) published a special 

 article on " Medusae fosforische " and included the work in his 

 Viaggi alle due Sicilie (1793) .-^ 



After a detailed description of the anatomy and a study of the 

 pulsation, Spallanzani directed his attention to the relation between 

 luminescence and movement. He had noticed that the light was 

 much brighter during systole than diastole and had previously ob- 

 served luminescence in the worm, Nereis marina, when it moved, 

 and lighting of the glowworm with each oscillation of the body. He, 

 therefore, concluded that it was probable the increase in brightness 

 on systole resulted from a stimulation of some kind which set off 

 pulsation and luminescence simultaneously. Many observers since 

 then, for example Quatrefages in 1843 and 1850, and S. Watase as 

 late as 1898, have called attention to the relation between movement 

 and luminescence. However, this relationship is not fundamental, 

 for an undisturbed Pelagia, swimming quietly through calm water 

 does not spontaneously luminesce with every pulsation. 



Taking medusae to his house where they were kept in large glass 

 vessels, Spallanzani noted that the light continued after death, when 



^^ Banks observed Medusa pellucens on November 29, 1768. Journal, ed. by J. D. 

 Hooker, 21, 1896. The Forskal (Descript. aniin. itin. orient, 109, 1775) , Medusa has 

 been identified as Pelagia noctihica. Sparmann (1772) and Schwarz (1789, 1792) are 

 quoted from Ehrenberg (1834, 435 and 438-439) . 



^''English translation. Travels in the two Sicilies, London, 1798. 



