No. 633] SHORTER ARTICLES AND DISCUSSION 



383 



The histology of the photophores of Porichthys notatus has 

 been reported upon in detail by Greene (1899), and ten years 

 earlier by Eigenmann and Eigenmann (1889), and by Test 

 (1889). These organs were found by the writer to be com- 

 pletely and typically developed in young about 25 mm. long 

 (sectioned at Stanford University). Each photophorc lies deeply 

 imbedded in the dermis. It consists essentially of a more or 

 less parabolic reflector surrounded by a mass of melanophores, 

 and enclosing Hie photopenic gland cells, which are richly sup- 

 plied with blood vessels, but according to Greene not speciiically 

 enervated. The light passes downward either directly from 

 these cells, or indirectly from the reflector, through the large 

 lens and the cornea-like epidermal covering of the organ. The 

 ventral aspect of the illuminated fish is striking, the hundreds 

 of dots of light being arranged in a symmetrical pattern. 



The light of Porichthys has been observed only in the labora- 

 tory, where it has been produced as a response to intense elec- 

 trical or chemical stimulus. Green records but one instance of 

 a slight glow of the photophores being produced by mechanical 

 stimulus. In experimenting with two specimens from rather 

 deep-water, the same author was unable to produce any reaction 

 of the photophores, although he applied stimuli successful in 

 the case of individuals from the reefs. This observation, while 

 of course insufficient, perhaps indicates that the luminescence may 

 be characteristic of the breeding season. In this connection it 

 is also significant to note that Holder's observations (Holder and 

 Jordan, 1909) indicate that the species is of nocturnal habits, its 

 enmtih". being heard chiefly at night, or in the evening or early 

 morning. 



The peculiar humming sound produced by this species during 

 the night, or during the day when disturbed, is another of its 

 remarkable characteristics. The sound (which by some has been 

 called a "song." an expression which seems quite figurative) is 

 produced in the air-bladder, which has a very thick muscular 

 wall, and is enervated by the thickest ramus of each vagus nerve. 

 Upon opening a live specimen the air-bladder was observed by 

 the writer to vibrate rapidly while the fish was grunting, and 

 the sides of the body were felt vibrating at the same time. The 

 abdomen of young about 25 mm. long was also felt vibrating, but 

 the sound produced, if any, was inaudible. 



