ANIMAL PHOSPHORESCENCE. 455 



patch, a centimetre or so long, break out in the middle of an arm, and 

 travel slowly out to the jtoint, or the whole five rays would light up at 

 the ends and spread the fire inward. Doubtless, in a sea swarming 

 with active and predaceous crustaceans, with great bright eyes, phos- 

 phorescence must be a very fatal gift. On one occasion the dredge 

 came up tangled with the long pink stems of a kind of sea-pen, which 

 were resplendent with a pale lilac phosphorescence like the flame of 

 cyanogen gas ; not scintillating like the green light of the star-fish, 

 but almost constant, sometimes flashing out at one point more brightly, 

 and then dying into comparative dimness, but always sufliciently 

 bright to make every portion of a stem caught in the tangles or stick- 

 ing to the ropes distinctly visible. In some places, nearly everything 

 brought up seemed to emit light, and the mud itself was perfectly full 

 of luminous sparks. The sea-rushes, the sea-fans, and usually the sea- 

 pens, shone with a lambent, white light, so bright that it showed dis- 

 tinctly the hour on a watch. In the neighborhood of the Madeiras, 

 jelly-fish have been taken which emitted light in flashes, and the 

 same phenomenon has been noticed in other parts, both in respect 

 to jelly-fish, and, as we shall see, in respect to other animals. 



Some of the most beautiful, luminous phenomena of the ocean are 

 caused by animals belonging to the molluscous sub-kingdom, which 

 is nearly as prolific in light-giving species as the Radiata. There is a 

 shell-less mollusk which inhabits the Atlantic, in the neighborhood of 

 the equator, and resembles a tiny cylinder of incandescent matter. It 

 is microscopic in size, but prodigious numbers adhere together, until 

 a tube from five or six to fourteen inches in length is formed, and the 

 sea sometimes presents the appearance of a sheet of molten lava, from 

 the number of these tubes which are floating in it. Moreover, a sin- 

 gular phenomenon is connected with this form of phosphorescence : 

 the color of the light is constantly varying, passing instantaneously 

 from red to brilliant crimson, to orange, to greenish, to blue, and 

 finally to opaline yellow. Another highly phosphorescent species of 

 Mollusca belongs to the family of the Salpidm^ which abounds in the 

 Mediterranean and the warmer parts of the ocean. These individuals 

 also swim adhex'ing together in vast numbers, and produce the efiect 

 of long ribbons of fire, sometimes drawn straight in the direction of 

 the currents, sometimes twisted and almost doubled by the action of 

 the waves. In the Mediterranean their phosphorescence often resem- 

 bles the light of the moon, giving rise to what the French term une 

 mer de lait. 



Luminosity is not so frequent a characteristic of the marine Articu- 

 lata ; nevertheless, it is exhibited by certain worm-like animals be- 

 longing to the class Annelida, and by a large number of the smaller 

 Crustacea. In many instances the light takes the form of vivid scin- 

 tillations similar to those emitted by the Medusae, or jelly-fish, already 

 mentioned. The appearance is sometimes very brilliant, when great 



