DEEP-SEA FISHES. 303 



developed. On the other hand, this supposition is opposed by 

 the fact that many fishes which dwell in those abyssal depths 

 are provided with large ordinary eyes (as the Traehypteri, the 

 majority of Macruridce), and, therefore, that the ordinary 

 organ of vision is quite sufficient for seeing by phosphores- 

 cent light. Thus, whilst we must admit that those compound 

 organs may prove to be organs of sense, we maintain at tlie 

 same time that their morphological nature is not opposed to 

 the belief that they too, like the glandular organs, are pro- 

 ducers of light. It may be produced at the bottom of tlie 

 posterior chamber, and emitted through the lenticular body 

 in particular directions, with the same effect as light is sent 

 through the convex glass of a " bull's eye." This hypothesis 

 seems to be less bold than the other, which would require us 

 to believe that vertebrate animals, with a nervous centre 

 specialised for the reception of the impressions of the higher 

 senses, should receive them through the spinal chord. 



[See Ussmo, "Ueber den Bau der sogenannten augenaehnliclien Flecken 

 einiger Knoclienfisclie." St. Petersburg, Bullet. 1879.] 



Whenever we find in a fish long delicate filaments, de- 

 veloped in connection with the fins or the extremity of the 

 tail, w^e may conclude that it is an inhabitant of still water 

 and of quiet habits. Many deep-sea fishes {Trachyptcridce, 

 Macruridce, Ophidiidcc, Bathyptcrois) are provided with such 

 filamentous prolongations, the development of which is per- 

 fectly in accordance with their sojourn in the absolutely 

 quiet waters of abyssal depths. 



Some of the raptatorial Deep-sea fishes have a stomach 

 so distensible and capacious that it can receive a fish of 

 twice or thrice the bulk of the destroyer {Melanocetus, Chias- 

 modus, Saccopharynx). Deglutition is performed in them 

 not by means of the muscles of the pharynx, as in other 

 fishes, but by the independent and alternate action of the 



