REPORT ON THE DEEP-SEA FISHES. 283 



II. THE DIVERSITY OF THE PHOSPHORESCENT ORGANS. 

 The following species were examined by me : — 



Opostomias micripnus. 

 Echiostoma barbatum. 

 Pachystomias microdon. 

 Malacosteus indicus. 

 Astronesthes niger. 



Argyropelcc us hemigyinnns. 

 Sternoptyx diaphana. 

 Scopelus benoiti. 

 Xenodermich thys nodxdosus. 

 Halosa urns macrochir. 



Halosaurus rostratus. 



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

 and all the various forms described by Ussow, Leydig and Emery, are represented in (jne 

 or more of them. 



I distinguish twelve different kinds of phosphorescent organs in these fishes, whicli 

 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, regulax*, bulbous organs sunk into the body are met with, 

 which have been designated by Ussow as " augenahnliche Organe" and )jy Leydig as 

 "augeniihnliche " and "glasperleniihnliche " organs. 



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

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

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

 compound regular ocellar phosphorescent organs, are particularly the ones considered as 

 "augenahnliche" and " glasperlenahnliche " organs by the authors mentioned. 



The simple ocellar organ is more or less s^iherical, 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 tlien their spherical 

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

 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, Ijut they ma}- (U' may not be 

 provided with a layer of threads or spicules, which shine like silver, refract the light 

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

 with Leydig's " glasperleniihnliche " organs. They are always very ol)lique to the surface, 

 whilst those which are destitute of a light-reflecting layer ajipear generally more or 

 less perpendicular to the outer surface. 



