THE EYE-LIKE ORGANS OF FISHES. 



167 



number of which stream out over the spherical circumference of the 

 sack, and fill the neck-part debouching without, so as to give the fig- 

 ure of a cone of rays sunk into the sphere. The net-work is, like that 

 of the orange, filled with small cells, a part of them strongly refract- 

 ing the light, which pass toward the common point of radiation of 

 both divisions into an opaque granular substance. A nerve is always 

 present in the neck-region of this organ, the fibers of which appear to 

 be lost in the granular midst of the spherical section whose exact his- 

 tological relations have not been ascertained. Externally, the whole 

 organ is inclosed in a lymph-chamber. 



The glass-pearly organs are also distributed over the sides of the 

 belly, the head, the gill-flaps, and the skin of the gills, and the three 

 on the skin of the gills are always longer than the others. They are of 

 the shape of a round disk a little sunken, with a body having a metallic 



Fig. 3 Ete-ltke Organs from the Bor- Fig. 4. Longittdtnal Section of the Eye of 

 der of the Bsli.y of A>'qyropelecus hemi- Stomiis anguiUiformis (after Des-sow), with the 

 gymnus; longitudinal section, greatly mag- p.-irts designated thu* : interior vitreous eub- 

 nified. stance (ir): lens (D\ retina ir) ; pigment layer 



(p) : iris-like fold {if), and opiic nerve (n), 

 greatly magnified. 



luster and overlaid with a curved transparent integument. An outer 

 brown film of pigment is always present, with a layer of closely joined, 

 regular, hexagonal plates, and a latticed jelly-tissue of delicate, radi- 

 ated cells that form a net-work, and are lifted up under a roof -like, 

 spiral-shaped concretion (Fig. 5). The nerve-bundles are also present. 

 Quite similar, but distinguished chiefly by their larger size, is the struc- 

 ture of the so-called luminous organs which are present in the Scope- 

 lus Rafinesquii and Scopelus metopoclampus as brightly glittering, 

 w T ell-detined spots above the nasal openings and under the eyes, and 

 which in Scopelus Humooldtii and Scopelus JBenoitii exhibit the form 

 and appearance of depressed pearl-spots. 



