102 THE VICTORIAN NATURALIST. 



the glandular cells are radial canals, backed by a thin layer of 

 pigment which serves as a reflector. In the compound organ (3) 

 there is not only the glandular secretion present, from which the 

 light comes, but in addition two chambers with radial canals, and 

 a lens-like body in front, all of which serve to intensify the light. 

 This organ has a double surface, as it were, for the line of pig- 

 ment, and therefore more surface for reflection. 



One especially curious deep-sea fish was discovered by the 

 Challenger off the coast of Brazil. This was Ipnops murrayi. No 

 eyes are present, but in their place are two structures which 

 Professor Moseley showed to have the power of producing light. 



Sometimes the organs are arranged regularly along the lateral 

 line, taking the place of the ordinary lateral line sense organs. 

 This is seen in Odontostomus, which also has small organs on 

 the head. In one species, which Alcock called Lamprogrammus, 

 or " line of radiance," the scales are hollowed out and contain a 

 greasy white substance, the oxidation of which appears to cause 

 the light. Many writers have compared fish such as this one to 

 miniature ships, with rows of port-holes lighted up, but we must 

 remember that most of these really are miniature, as the fish are, 

 for the most part, very small — about one and a half to twelve 

 inches long. 



Among the deep-sea fish we also have the anglers, just as 

 among fish of shallow water. In these, however, instead of the 

 lure which looks like an attractive morsel hanging in the water, 

 we find a lantern. In Onirodes, which is only about 2 inches in 

 length, there is a glandular luminous mass placed at the end of 

 the modified first dorsal fin ray. This fish is blind, but its light 

 attracts smaller fish, and so to obtain its food it simply has to 

 wait and hold its mouth open. 



I think enough has now been said to show how exceedingly 

 varied and numerous are the cases of phosphorescence in 

 animate nature ; but the questions which now arise are — What is 

 the light due to? and what is its use in the economy of the 

 organism ? Many answers have been attempted to these 

 questions in the past, but the man of science to-day is very wary 

 in attributing a cause, no matter how he may speculate as to the 

 possible uses to the animal. Without going into the many 

 theories which have been suggested as to cause, the light is 

 certainly always associated with oxidation, and in many cases 

 probably with the oxidation of fats. 



As to the possible uses of phosphorescence to the animal, 

 Morgan (26) suggests that it is of no use, the phenomenon being, 

 according to him, only a by-product of changes going on in the 

 cells, and having no relation to outside conditions. This certainly 

 seems to be the case with bacteria, but probably nowhere else. 



Why should eyeless fish use light ? With such forms it evi- 

 dently is a bait to attract their prey. For others which have 



