LAMl'ROGRAMMUS ILLUSTRIS. 175 



Lateral line as wide as the orbit, extending back on abont eighty scales 

 to a point below the seventy-fifth dorsal ray. It might be described as 

 apparently composed of two systems; the ordinary one below and through 

 the scales, and a luminous system outwardly resembling a dermal tube cov- 

 ered by about eight series of smaller very thin scales and appljed to the out- 

 side of a couple of series of the larger scales of the flank two or two and one 

 lialf scales from the base of the dorsal fin. This tube, Plate XXXIV. fig. 

 4, contains mucus and against its inner wall a series of narrow, spindle 

 shaped, vertically placed, glandular light or flash organs, Plate XXXIV. 

 figs. 1, 3, 4, 5, connected with one another by a fine nerve-like strand of 

 tissue. Each of the luminous organs is fusiform, somewhat flattened, taper- 

 ing- at each end and enlarged in the middle, where it contains an elliptical or 

 rounded body, disk or facet, of different structure, Plate XXXIV. fig. 5. 

 From each end of the spindle the tissue appears to be reflected around the 

 wall of the tube over the gland so as to form a complete ring. While the 

 skin and scales covering the structures present a black appearance in the col- 

 lapsed condition both are so thin as to offer little obstruction to the passage of 

 liglit when the tube is distended by mucus. On Lamprograminus mgei\ Alcock, 

 1891, Ann. Mag. N. H., VIII., 34, describes loopholes over the glands; no 

 such openings are to be seen on the present species. The pores in places 

 appear to open along the lower edge of the tube away from the organs. 

 Each organ of the series rests on a large scale twice as wide as those at each 

 side of it and separated from similar organ-bearing scales by a pair of the 

 ordinary scales of the flank, half as large, Plate XXXIV. fig. 4. Thus the 

 light organs on this species are not on contiguous scales, as figured on L. niger, 

 in the Annals and Magazine, 1891, VIII., p. 33, or in tlie Illustrations of 

 the Zoology of the ''Investigator," 1892, Plate I. fig. 2; the differences will 

 be prominently shown by comparison of the mentioned illustrations with 

 Plate XXXIV. of the present work. It is most likely that the large scale 

 bearing the spindle was originally an ordinary small scale which has so 

 enlarged as to cover its neighbors in the next series. The body between the 

 lateral systems of the two sides is thinner than either above or below them ; 

 this gives rise to the groove-like depressions occupied by the lines. Behind 

 the line on the tail the groove disappears and the squamation is irregular. 

 The luminous system originated on the head and gradually extended back- 

 ward over the body ; the arrangements of the scales are suflflcient evidence 

 that it is a later development. 



