2318 Bulletin ^7, United States National Miiseum. 



resemblance. These so-called phosphorescent organs are arranged in rows over the body, 

 and are definite and characteristic and quite constant in location in different individ- 

 uals. They are accompanied by rows of epidermal sense organs, the two having an inti- 

 mate relation in distribution over the surface of the fish. In surface view the shining 

 organs have a bright silvery appearance, are more or less round in outline, size from a 

 mere dot to 0.8 mm. in diameter, and surrounded or bordered on one side by an increased 

 amount of pigment. The end buds present a round, transparent, or pellucid, and usually 

 slightly raised, point. Each end bud is bordered by a pair of papillae. There are about 20 

 well-defined lines as follows : The lateral row, from posterior upper border of pectoral 

 straight alongside to upper third of base of caudal, 35 pairs with an end bud between each 

 pair, upper series small or rudimentary, segmentally arranged and between myomeres. 

 Thepleuralrow, from middle of base of pectoral, curves backward and downward to a 

 point above first anal ray then straight nearly to base of caudal, 43 to 62 organs. End 

 buds below each organ to above middle of caudal, 31 organs. The caudal rows, end buds 

 only, 2 longitudinal rows on upper and lower thirds of fin. The anal row, on either side 

 base of anal fin from third anal ray to base of caudal. Phosphorescent organs in pairs, a 

 pair for each anal ray, 1 end bud for each pair. The gastric row, from front around lower 

 edge of pectoral and along side of belly to opposite anal papilla, 30 phosphorescent 

 organs. The gular row, from isthmus along ventral side of ventral fin then outward to 

 join gastric row, spur runs forward along external side of ventral fin, 27 organs. A par- 

 allel line of 50 end buds follows the gular row and posterior end of gastric. The ventral 

 row with its fellow forms a parenthesis on the stomach from the side of the anus J the 

 distance to the ventral fin, 34 organs ; no end buds. The branchiostegal row, from the 

 . isthmus outward over branchiostegal membrane and between first and second rays, no 

 end buds. The mandibular row of phosphorescent organs extends around inner edge of 

 ridge formed by the dentary bones; the row of end buds along the outer rim of the same 

 ridge. The opercular rows, upper and lower, extend backward and upward across opercle. 

 The scapular row, from above opercular spine straight back above pectoral fin, the curves 

 in toward the base of the dorsal fin opposite the third dorsal ray. The dorsal row, along 

 base of dorsal fin to base of caudal. This row and the scapular row consist of well developed 

 end buds and rudimentary phosphorescent organs. The occipital and frontal rows, along 

 the occipital and frontal regions, short rows of small and poorly developed organs. The 

 nasal, from the posterior nasal tube to base of anterior tube. The suborbital and post- 

 orbital, from posterior nasal opening around under eye backward and downward to oper- 

 cle. A malar row, from the suborbital down across the cheek. A maxillary across the 

 posterior end of maxillary bone. The rows on the head consist of well-developed end 

 buds with rudimentary and irregularly placed phosphorescent organs. The phosphor- 

 escent organs are embedded in the connective tissue dermis of the skin, and in section 

 show a uniform general structure throughout the body. A typical organ from the anal or 

 ventral rows consists of an outer spherical group of cells called a lens, resting in a deeper 

 cup-like structure, the capsule, and this in turn in a cup of fibrillar connective tissue 

 called the reflector. The lens consists of cells, polygonal in the center of the group and 

 flattened or fusiform around the periphery. They have a large conspicuous nucleus and 

 a dense, homogeneous, highly refracting cell body. The outlines of the cells are very 

 distinct. In the cells of the capsule the nuclei stain readily, but the granular protoplasm 

 with difficulty, and the cell boundaries are indistinct and usually obliterated. In some 

 specimens connective tissue septa penetrate the capsule. Blood capillaries are arwavs 

 present. The reflector extends well up around the sides of the lens ; it consists of 

 fibrillar connective tissue which strongly reflects light. Much pigment is embedded in 

 its meshes. No nerves have yet been traced to the organ. The developing phosphor- 

 escent organs do not appear in the embryo fish until it is 15 to 16 mm. long. Then a bud 

 appears in the lower layer of the epidermis, which soon becomes constricted off as a 

 spherical mass of shells lying in the snbepidermal connective tissue. This mass later 

 slightly elongates and gives rise by constriction to the lens and the capsule. Tho 

 reflector is developed from the surrounding connective tissue, so also the pigment cells. 

 Mature organs are not found until the fish reaches a length of over 20 mm. The end buds 

 appear much earlier, 9 to 10 mm." (Charles "Wilson Greene.) 



