a as 
THE RADIATING ORGANS OF THE DEEP SEA FISHES. 178 
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, 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 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 Sternopiyx hermanni “ flotait renversé sur 
le cote.” Garman (1. ¢.) does not mention the occurrence of any difference 
in the coloration of the two sides in A. lychnus, nor have I noticed it. 
However the case may be with A. hemigymnus I do not think it likely that 
A. lychnus swims on its side. In a previous paper (87, pp. 803-307) I have 
described the radiating organs of A. hemigymnus and other fishes, in which 
they have a similar structure. The fibrous layer in the organs of A. hemu- 
gymnus was found to contain parallel and longitudinally arranged fibres 
of considerable length; so there is no difference between these species 
and A. dychnus in this respect. The statement there made that the inner 
region is composed of tubes “ned with glandular cells does not apply to A. 
lychnus, 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. hemigymnus, 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 efferent ducts. These cells produce 
a seeretion 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. 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. Te 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 
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