THE RADIATING ORGANS OF THE DEEP SEA FISHES. 173 



enter it at various points. The stoutest nerve branch enters the organ at 

 the constriction between tlie oval and conic parts. The cells composing the 

 inner region are described as arranged in columns. Leydig suggests (1. c, 

 p. 38) that the fish may swim on its side like a pleuronectid, and not verti- 

 cally. He supports this view by stating that tlie pigment is not eiiuall^- 

 developed on the right and left side and by quoting a statement of Valenci- 

 ennes to the effect that the similar Stcrnopt//x /lernuauu "flotait renversr sur 

 le cote." Garman (1. c.) does not mention tlie occurrence of any difference 

 in the coloration of the two sides in ui. li/chaus, nor have I noticed it. 

 However the case may be with A. /ieii/itj//inims T do not think it likely that 

 A. l//chmts swims on its side. In a previous paper ('87, pp. 303-307) I have 

 described the radiating organs of A. hemigi/mmis and other fishes, in which 

 they have a similar structure. The fibrous layer in the organs of A. lu'iiil- 

 (jpnmis was found to contain parallel and longitudinally arranged fibres 

 of considerable length ; so th^re is no difference between these s^aecies 

 and A. If/chius in this respect. The statement there made tliat the inner 

 region is composed of tubes lined with glandular cells does not apply to A. 

 lijchwii, where such tubes could not be made out ; there is hardly even a 

 trace of the columnar arrangement described by Leydig. 



Brandes ('99, p. 470), who also described A. licmigjjmnus, says that the 

 anteorbital organs are connected with muscles and can be moved about at 

 will so as to throw their radiation in any direction the fish may choose. 

 This statement has been contradicted Ijy Handrick ('01, p. 54). The fibre 

 .sheath consists of long and slender tissue cells containing guanin and lime. 

 Tiie tissue of the inner region is, according to Brandes ('99, p. 484), composed 

 of roundish gland cells and is without efferent ducts. Tliese cells produce 

 a secretion which, according to Brandes, disintegrates chemically and thereby 

 emits light. The light passes the middle region, considered by him as a 

 biconcave lens, and illuminates the gelatinous mass which occupies the 

 outer region, and which is backed by the inner face of the distal part of 

 the reflecting fibre layer, 'i'hus the luminosity would be visible chiefly 

 from ]ioints at the side of the fish. 



Chiarini ('00, pp. 7-10, Figs. 1, 4, G) has likewise studied the organs In A. 

 hemigpnuus. He reproduces a figure (1) of an axial longitudinal section of 

 one of them, which — apart from its being upside-down — closel}- corrt^ 

 spends to the figure of a similar section of the anterior laternl organ in ^4. 

 l^chiitts here given (Plate 6, E'ig. 24). According to Chiarini the pigment 



