322 EUPERT VALLENT1N AND J. T. CUNNINGHAM. 



Luminosity of the Ocean, with descriptions of some remarkable 

 species of Phosphorescent Animals, and particularly of the 

 four new genera— Noctiluca, Cynthia, Lucifer, and Podopsis of 

 the Schizopodae." In this memoir he relates how he captured 

 the species he calls Noctiluca in the Atlantic, on his voyage 

 home from the Mauritius, and says the animal gave out bril- 

 liant scintillations in the dark when disturbed. It was inmost 

 parts perfectly transparent, but turgid here and there, with 

 orange-red pigment, particularly on its anterior feet. 



Thomson identified his specimens with a form described by 

 Sir Joseph Banks, and observed by him to be luminous, and to 

 be the chief cause of the phosphorescence of the sea on a cer- 

 tain occasion. Banks gave the animal the name Cancer 

 fulgens,. which Thomson altered. The latter was quite 

 unaware that the luminosity was due to and limited to special 

 organs, and makes no mention of any ''accessory eyes," 

 although there is little doubt that his Noctiluca (which has not 

 yet been identified with one of the species now recognised) 

 belonged to the family Euphausiidse. 



The naturalists on board the " Challenger" were familiar 

 with the phosphorescence of the Euphausiidse, and observed the 

 connection between the emission of light and the organs 

 known as accessory eyes. 



Mr. John Murray paid particular attention to animal phos- 

 phorescence and to the captures of the tow-net, and therefore 

 was repeatedly impressed with the brilliancy of the luminosity 

 of members of this family, and its exclusive origin in the 

 special organs. 



The account given in the ' Narrative of the Cruise of the 

 " Challenger" ' (vol. i, p. 743) is as follows : 



" The phosphorescent light emitted by the species of 

 Euphausiidse was frequently under observation during the 

 cruise. If one of these be taken up by a pair of forceps when 

 newly caught, a pair of bright phosphorescent spots will be ob- 

 served directly behind the eyes, two other pairs on the trunk, 

 and four other spots situated along the median line of the tail. 

 These can all be quite well seen by the naked eye. The pair 



