2 THE NATURE OF ANIMAL LIGHT 



colonies, and we now know that the light of all dead fish 

 and flesh is due to luminous bacteria. 



In the early part of the nineteenth century it was sur- 

 mised that the light of damp wood was connected with 

 fungus growth because of a similarity in smell. In 1854 

 Heller recognized minute strands, which he called RJiizo- 

 morplia noctiluca, as the actual source of the light. We 

 now know that all phosphorescent wood is due to the 

 mycelium of various kinds of fungi and that sometimes the 

 fruiting body of the fungus also produces light. 



The phosphorescence or ^'burning of the sea,'^ which 

 is described by so many of the older explorers, is also due 

 entirely to living organisms, both microscopic and macro- 

 scopic. The latter are mostly jelly-fish (medusce) or comb 

 jellies (CtenopJiores) and give rise to the larger, more bril- 

 liant flashes of light often seen in the wake or about the 

 sides of a steamer at night. The former are various 

 species of dinoflagellates or cystoflagellates such as 

 Noctiluca (just visible to the naked eye) which collect 

 at the surface of the sea and often increase in such num- 

 bers that the water is colored by day (usually pink or 

 red) and shines like a sheet of fire when disturbed at night. 

 Although Noctiluca was recognized as a luminous animal 

 in 1753 by Baker, the light of the sea was a mysterious 

 phenomenon to the older observers. MacCartney, speak- 

 ing before the Royal Society in 1810, outlines the various 

 older theories as follows : * ' Many writers have ascribed 

 the light of the sea to other causes than luminous animals. 

 Martin supposed it to be occasioned by putrefaction; 

 Silberschlag believed it to be phosphoric; Prof. J. Mayer 

 conjectured that the surface of the sea imbibed light, 

 which it afterwards discharged. Bajon and Gentil 



