LIVING LAMPS 233 



body and the head emitted a vivid greenish phosphorescent 

 gleam, imparting to the creature a truly ghastly and terrific 

 appearance. In all these little sharks the light is given off 

 from large areas of the skin, especially on the lower side and 

 head. 



More than two dozen different types of light emitting organs 

 are found among the fishes, some very simple, others exceed- 

 ingly complex with a structure more or less like that of eyes, 

 but fitted to send out light rays instead of to receive them. 

 Indeed, the eyes themselves may be transformed into phos- 

 phorescent organs. Luminous organs in the fishes are situated 

 mostly on the head, or on the head, sides, and low^er surface. 

 Many fishes have rows of little lights along their sides so that 

 they look like Httle steamers with all the port holes lighted. It 

 is a very curious fact that many of the luminous fishes are 

 wholly blind. 



If you stand at a steamer's stern at night and watch the 

 myriads of sparks and flashes in its wake you will see from 

 time to time large and brilliant glowing objects usually a foot 

 or so in length. These are the Pyrosomas or "fire-bodies," each 

 a hollow C}'linder made up of very many little tunicates all 

 growing close together. You find these in all seas over deep 

 water, though they are scarce and rather small in the Caribbean 

 and in the Gulf of Mexico, and they disappear completely in 

 the mid-Pacific. Of the Pyrosomas not all kinds are luminous, 

 though most of them seem to be, and when they are they are 

 extremely brilliant, appearing as cylinders of fire, reddish, yel- 

 lowish, blue or greenish, sometimes appearing as of mixed 

 colors. Professor Huxley found that a Pyrosoma he examined 

 was at its brightest red, fading through shades of orange, green 

 and blue. When suddenly shaken by the passage of a steamer 

 a Pyrosoma lights up all at once and glows for a considerable 

 time. If one be taken in the hand the portions touched im- 

 mediately light up and the illumination spreads, increasing in 

 intensity, in all directions until the whole mass is aglow, then 

 slowly fades away, with occasional local waves of brightness. 



