THE RADIATING ORGANS OF THE DEEP SEA FISHES. 203 



/. murrat/i, and has examined and carefully described their minute struc- 

 ture. In the material of /. atjassizii at my disposal these discs are not suffi- 

 ciently well preserved to allow of their minute structure being studied. 

 All I can say is that I have seen nothing in them that would justify one in 

 supposing that they differed in any way from the organs described by 

 Moseley in /. murrcuji. The hexagonal cylinder cells of the discs of /. 

 agassidi are about 20 /x long and 5 /x thick. 



(3) THE FISHES WITH TUBULAR RADIATING ORGANS. 

 MalthopsiS spinulosa Garman. 



Plate 1, Figs. 1, ^, Plate 2, Figs. 6-9. 



This species has been described by Garman ('99, p. 106, Plates 21, 24). It is 

 (Plate 1, Figs. 1, 2) a flat fish of horseshoe-shape with a stout conic tail. 

 The organ here to be described which may have a radiating function is 

 a medial tentacular papilla on the forehead just above the mouth (Plate 2, 

 Fig. 6 te). Garman ('99, p. 106) states that this papilla is contractile and 

 can be extended and retracted at the will of the fish. In the state observed 

 by me it is about 6 mm. long and 1.5 mm. thick. This papilla is situated in 

 a depression so that it protrudes when retracted only slightly beyond the 

 general surface of the fish. The apex of the papilla is divided into three 

 lobes, an upper somewhat leaf-shaped one and a pair of lower massive 

 ones. 



The trilobed terminal part of the tentacular papilla of the only specimen 

 of Malthopsis spinulosa at my disposal was cut into a series of transverse 

 sections. These (Plate 2, Figs. 7, 9) show that its trilobed distal part is 

 supported by four stout longitudinal rods of semicartilaginous tissue (Figs. 

 8, 9 s). The two lower ones are separate, the two upper ones joined to 

 form a band-shaped structure. These rods are enclosed in sheaths of con- 

 nective tissue from which septa (Figs. 7, 8, 9 c) radiate, chiefly into the 

 massive ventral lobes, the interior of which is divided by them into a 

 number of longitudinal compartments. In the middle of the ventral surface 

 connecting the two ventral lobes a conspicuous longitudinal ridge is ob- 

 served, the interior of which is occupied by a pair of longitudinal muscles, 

 lying close together (Figs. 8, 9 m). These are, no doubt, the muscles which 

 retract the tentacular papilla, while its extension is probably brought about 



