PHOTOSPHERIA OF NYCTIPHANES NORVEGICA. 337 



ing surface, and this is morphologically a modified dermic 

 scale. There is a special kind of cell often present which 

 Lendenfeld regards as a specialised gland-cell. Each of these 

 contains a highly refractive vesicle which represents the secre- 

 tion of the gland-cell. 



To take one or two examples. One of the most interesting 

 of the organs described is that called " ocellar, regular, com- 

 posite." Some of these are provided with a reflecting layer 

 internal to the pigment, composed of calcareous spicules, and 

 morphologically comparable to one or more scales. These 

 organs are all formed on one general plan. There is a spherical 

 deep portion surrounded externally by pigment, and continued 

 towards the surface of the animal into a superficial portion, 

 which is either a paraboloid or a parabola in some of its sec- 

 tions. The interior of the spherical portion is occupied by 

 gland-tubes usually arranged radially, and lined by a single 

 layer of gland-cells. Where the gland-tubes converge there is 

 a space into which they pour their secretion. In the organs 

 with reflectors cords composed of blood-vessels and nerves 

 pierce the calcareous reflecting layer and extend vertically to 

 the surface. These vertical columns are surrounded by ra- 

 diating, slender cells, closely packed, so that each column of 

 nerves and muscles forms the core of a cellular prism. Some 

 of these slender cells are thin and inconspicuous, but among 

 them are large club-shaped cells, which contain an oval, highly- 

 refractive body, the latter apparently consisting of a cavity 

 with a very fine wall, and containing fluid. The cellular 

 prisms are separated from each other by a kind of packing 

 composed of small cells, and the surface is also covered by 

 layers of these cells. These organs are almost the only ones 

 from which light has actually been observed to be emitted. 

 Guppy 1 saw the light emitted from them in Scopelus. Len- 

 denfeld thinks that the deeper gland-tubes pour out a slimy 

 secretion into the distal portion, and that a mutual chemical 

 action takes place between this slime and the typical phos- 

 phorescent clavate cells above mentioned, at the will of the fish, 

 1 Ann. and Mag. Nat. Hist.,' ser. 5, vol. ix. 



