THE EYE-LIKE ORGANS OF FISHES. 



165 



our recognized sensorial functions, but rather point to some sixth sense, 

 unknown to us. To this class belong the phenomena presented by a 

 group of bony fishes, living for the most part at extreme sea-depths, 

 classified in the three related families of the Scopelids, Sternop>tychids> 

 and Stomiatids, which have lately received attention from naturalists. 

 They are generally small fishes, often only an inch or less in length, 

 and have on either side of their belly a row of bright spots, extending 

 from the snout to the tail, that might be said to look like a double row 

 of pearl-buttons fastened upon their skin-coat. Sometimes a third row 

 is found extending from the head to the anal fin ; and frequently single 

 spots, often of considerable size, are scattered over the head and gills 

 and over the sides of the fish. Several ichthyologists among them B. 

 Rafinesque, of Palermo ; Delle Chiaje, of Naples ; Risso, of Nizza ; and 

 Cocco, of Messina have had their attention drawn, since the first dec- 

 ade of the century, to specimens of those creatures that have occasionally 

 been washed ashore in storms ; and the more recent deep-sea investiga- 

 tions have made several allied forms known. The old ichthyologists ap- 

 parently never examined the spots very carefully, but simply described 

 them as silvery mottles or light points. Leuckart seems to have given 

 them the first critical examination in 1864, in Chauliodus Sloani, Sto- 

 mias boa, and Scopelus Humboldtii, and came to the opinion from it 

 that they might possibly be regarded as supplementary eyes. Ussow, 

 of Moscow, published a paper in 1879 on the structure of the so-called 

 eye-like spots in Chauliodus, Stomias, Astronesthes, Gonostoma, and 

 Maurolicus, in which he expressed the conclusion that the spots in the 



Fig. l.Argyropekcus hemigymnus, twice the natural size. 



three first-named genera were real organs of sight, but that the struct- 

 ure of those in the other genera was of a quite different nature, and 

 really glandular. In the same year Leydig published a work on the 

 Chauliodus Sloani, in which he admitted the similarity of the spots 

 of that species to eyes, but was disposed to regard them as transitional 

 organs rather than as real eyes, and referred to one of his observations 

 as indicating that they might have been luminous in life. Leydig has 

 more recently examined ten other species of the families Sternopty- 



