204 THE RADIATING OEGANS OP THE DEEP SEA FISHES. 



by the elasticity of the semicartilaginons rods described above or the ac- 

 cumulation of blood in tlie large longitudinal, sinus-like bloodspace (Figs. 8, 

 9 b') which occupies the centre of the tentacular papilla. Other smaller 

 blood vessels (Figs. 8, 9 b) are met with in its superficial parts. 



The longitudinal chambers formed by the connective-tissue septa men- 

 tioned above, are large and dorsoventrally depressed in the dorsal leaf-like 

 part, whilst they are radially arranged like a fan in the two lower lobes. 

 The connective-tissue walls of these chambers are clothed by a high epithe- 

 lium composed of a single layer of cylindrical cells. In the sections this 

 cell layer (Figs. 7, 8, 9 pc) is, however, by no means in direct contact with 

 the connective-tissue walls, but separated from them by an apparently empty 

 space of considerable extent (Figs. 7, 8, 9). Thus these cylinder cells form 

 tubes lying within the likewise tubular chambers formed by the connective- 

 tissue septa. The lumina of these tubes (Figs. 7, 8, 9 cv) are narrow and 

 eitlier empty or occupied by a structureless mass, apparently a secretion. 

 The cylinder cells themselves contain a j^retty transparent protoplasm, which 

 is strongly stained witli picric acid, but hardly at all with haematoxjdin. 

 The large, oval, granular nucleus lies in the outer (lower) termination of 

 the cell. Pigment is found chiefly in the outer skin of the dorsal leaf-shaped 

 lobe. 



In structure these organs resemble the inner portions of the suborbital 

 organs o^ rach/domias microdon (Lendenfeld '87, p. 320-322, Plate 71, Figs. 

 30, 31), where however the cells forming the tubes are not so hisxh. It is 

 particularly to be remarked that also in this part of the suborbitals of 

 P. microdon one finds in the sections the tubes formed of these cells sepa. 

 rated from the connective tissue surrounding them, by apparently empty 

 spaces. 



Chun ('03, pp. 568, 569) has mentioned the occurrence of a frontal ten- 

 tacular papilla in other species of Mnlthopsis. lie thinks that the organ may 

 emit light, but is doubtful on this point. 



On the margin of the l)ody of this fish bud-like protruding organs of 

 peculiar structure (Plate 1, Figs. 1, 2, Plate 2, Fig. 6 o) occur, which I will 

 not describe here, being of the opinion that their function is not to radiate. 

 They are ramified, rich in l)lood vessels, and may be accessory gills, or .^euse 

 organs. These structures are dealt with in the Appendix. 



