THE EADIATING ORGANS OF THE DEEP SEA FISHES. 173 



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

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

 inner region are described as arranged in columns. Lejdig 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 the pigment is not equally 

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

 ennes to the effect that the similar Sternoptf/x hennanni " flotait renverse sur 

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

 in the coloration of the two sides in A. If/chniis, nor have I noticed it. 

 However the case may be with A. hemigymnus I do not think it likely that 

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

 described the radiating organs of A. hemigymims and other fishes, in which 

 they have a similar structure. The fibrous layer in the organs of A. hemi- 

 gymnus was found to contain parallel and longitudinally arranged fibres 

 of considerable length ; so there is no difference between these species 

 and A. lychmis in this respect. The statement there made that the inner 

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

 /^c/mz<6', 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. hemigymims, 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 by Handrick ('01, p. 54). The fibre 

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

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

 of roundish gland cells and is without efiferent ducts. These cells produce 

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

 emits light. The light passes the middle region, considered hy 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. Thus the luminosity would be visible chiefly 

 from points at the side of the fish. 



Chiarini ('00, pp. 7-10, Figs. 1, 4, 5) has likewise studied the organs in A. 

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

 one of them, which — apart from its being upside-down — closely corre- 

 sponds to the figure of a similar section of the anterior lateral organ in A. 

 lychnus here given (Plate 6, Fig. 24). According to Chiarini the pigment 



