REPORT ON THE DEEP-SEA FISHES. 283 



II. THE DIVERSITY OF THE PHOSPHOEESCENT ORGANS. 



The following species were examined by me : — 



Opostomias micripnus. Argyropelecus hemigymnus. 



Echiostoma barbatum. 

 Pachystoinias microdon. 

 Malacosteus indicus. 

 Astronesthes niger. 



^ Sternoptyx diaphana. 

 Scopehis benoiti. 

 Xeaodermichthys nodidosns. 

 Halosaurus macrochir. 



V Halosaurus rostratus. 



In these fishes a great many different kinds of phosplioresceut organs are met with, 

 and aU the various forms described by Ussow, Leydig and Emery, are represented in one 

 or more of them. 



I distinguish twelve difi'erent kinds of phosphorescent organs in these fishes, which 

 may be divided into two main groups. 



Scattered more or less regularly in segmental distribution over the ventral side or 

 the whole of the body, small, regular, bulbous organs sunk into the body are met with, 

 which have been designated by Ussow as " augcnalmliche Organe " and by Leydig as 

 "augeniihnliche " and "glaspcrlenahnliche " organs. 



I term these " regular ocellar phosphorescent organs." They may be " simple " or 

 "compound." The former correspond to those organs which are described as glandular 

 by Ussow and partly also to the " augeniihnlichen Organe " of Leydig. The latter, the 

 compound regular ocellar phosphorescent organs, are particularly the ones (,'onsidered as 

 "augeniihnliche" and " glasperleniihnliche " organs by the authors mentioned. 



The simple ocellar organ is more or less splierical, closed on all sides and generally 

 partly invested by a pigment coat ; its internal structure appears radial. 



The composite ocellar organ is divided into two parts, an interior closed spherical 

 portion divided by an annular incision from the cup-shaped external portion. Some- 

 times several of these composite organs stand close together, and then their spherical 

 basal portions may coalesce so as to form a canal or tube, to one side of which the i-up- 

 shaped outer portions of the joined organs are attached. 



The simple ocellar organs may or may not have a pigment coat. 



The composite organs always have a pigment coat, but they may or may not l)e 

 provided with a layer of threads or spicules, which shine like silver, refi-act the light 

 strongly, and act as refiectors. The composite ocellar organs with reflectors are identical 

 with Ley dig's " glasperleniihnliche " organs. They are always very oblique to the surface, 

 whilst those which are destitute of a light-reflecting layer appear generall}- more or 

 less perpendicular to the outer surface. 



