178 FISHES CHAP. 
mere mechanical laceration ; but, except the mucus secreted by 
the gland cells of the skin, which may possess venomous pro- 
perties, no special poison-forming glands in connexion with the 
spines are at present known. 
Phosphorescent Organs.’ 
In common with many other animals of similar habitat, 
phosphorescent organs (photophores) are highly characteristic 
structures in many deep-sea Teleosts belonging to widely different 
familes (e.g. Stomiatidae, Scopelidae, Halosauridae, and Anoma- 
lopidae). _ These organs probably had their origin in local aggre- 
gations of the gland cells of the epidermis, which had acquired 
the power of secreting a luminous slime. Luminous organs vary 
greatly in number and in their mode of distribution in the skin, 
Usually they are found on the sides and ventral surface of the 
body and head, very rarely on the dorsal surface, and they often 
present the appearance of brightly glistening jewels set in the 
skin. <A very frequent method of arrangement is in one or two 
longitudinal lines along the lateral and ventral surfaces, sometimes 
extending continuously from the head to the end of the tail (Fig. 
371, A, and Fig. 379), but occasionally interrupted and limited to 
portions of the body and tail; and in a few a distinctly meta- 
meric disposition is obvious. On the other hand, the very numerous 
and simple organs of Opostomias are disposed in many transverse 
bands along the sides of the Fish. In addition to these organs, 
which are usually numerous, and whose arrangement is linear, 
specially large and often structurally complex luminous organs are 
present on different parts of the head and body. In Opostomias 
micripnus there is a phosphorescent organ on a median barbel 
depending from the chin. Sternoptyx diaphana has one on the 
lower jaw. The presence of one or two organs beneath the eyes (Fig. 
96) is characteristic of several species (e.g. Opostomias micripnus, 
Astronesthes niger, Pachystomias microdon, Scopelus benortit, Mala- 
costeus indicus).  Opostomias micripnus has a luminous organ on 
the isolated and elongated first fin ray of the pectoral fin, while in 
certain deep-sea Angler-Fishes (e.g. Ceratias) there is one on the 
anterior cephalic fin-ray of the dorsal fin. The Scopelid Jpnops 
1 Lendenfeld, Chall. Reports, Zool. xxii. 1887, p. 277. For references to papers 
by Leydig, Ussow, Emery, and others, see Lendenfeld, op. cit. 
