PHOSPHORESCENCE OF THE SEA. 471 



(Fig. 622) and other Polypifera, the Pyrosoma (983) and other 

 Tunicata contribute to produce this dazzling effect, it is prin- 

 cipally due to the various species belonging to the group we are 

 now considering. 



1 030. The diffused luminosity is given by minute species ; 

 and on our own coasts it is principally due to the Noctiluca, a 

 little animal much resembling a grain of boiled sago in size and 

 appearance. The anatomy of this animal has not yet been satis- 

 factorily investigated, notwithstanding its occasional abundance ; 

 and its true place in the Class has not been ascertained. It 

 seems like a little granule of jelly, with a long stalk. This stalk 

 appears to be a trunk or sucking- tube, by which the food is taken 

 in ; and it is capable of being extended, or drawn in, to a con- 

 siderable degree. The luminous secretion appears in all instances 

 to become more vivid, when the animal is alarmed or stimulated 

 in any way. Hence the disturbance of the water, by the gentle 

 curling of the waves over each other, or by their ripple on the 

 shore, is marked by lines of increased brilliancy. The movement 

 of a boat, and the stroke of the oars, will have the same effect. 

 If the animals be washed over the sands, they continue to display 

 their luminosity in a fainter degree for some time ; but every 

 footstep of a person who walks over them is studded with bril- 

 liant points. And if the hands be dipped in the water thus 

 phosphorescent, and then rubbed together, they will be covered 

 with luminous spots ; which, when examined, are found to be 

 occasioned by the phosphorescent glow of these delicately-formed 

 little animals. There are few parts of the British coasts, where this 

 phenomenon is not occasionally witnessed. It generally follows 

 a continuance of some particular wind ; but the direction required 

 varies in different parts of our island. It is thus that we obtain 

 a more accurate idea of the vast amount of animals composing 

 this tribe, than we derive from any observations that can be made 

 during the day. Their bodies are often so transparent, that they 

 can scarcely be distinguished from the water through which they 

 are diffused, except when displaying their phosphorescence. But 

 when the whole surface of the ocean, as far as the eye can reach, 

 is seen to exhibit a uniform luminosity, and this is ascertained to 



