230 
POPULAR SCIENCE REVIEW. 
says that in this species there are from one hundred to one 
hundred and ten of these spots ; hut they differ in the point of 
covering scales, the presence of which is asserted by Ussow, 
while Leydig failed to detect their presence. This, however, 
is not a point of any great importance, and that the more since 
we know that in the Sternoptychidae, the family to which this 
fish belongs, the body is either naked or has only very thin and 
deciduous scales. 
Into the further details, as given by either of the his- 
tologists already named, it is impossible for us here to enter ; 
the student who desires to know more of the structural 
characters will gain a quantity of information from their 
works.* 
If we proceed to sum up briefly the general structure of 
these organs, we find that while IJssow speaks of them as 
accessory eyes or as glands, Leydig divides them into three 
groups ; (1) eye-like organs, (2) mother-of-pearl-like organs, 
and (3) luminous organs ; of these the second and third forms 
would seem to be peculiar to the genus Scopelus. 
The first set are saccular in form and divisible into a bulb, a 
neck, and an orifice, and this orifice is always directed down- 
wards. From what has been already said we know that they 
have an investment of brown pigment, a layer with a metallic 
glitter, a grey inner body, and a surrounding lymphatic space. 
The investment is derived from the general integument of the 
body, and the pigment granules are contained in the cells of the | 
underlying connective tissue ; the metallic layer consists of iri- i 
descent plates, rods, or fibres. The grey inner body is divisible 
into two portions, the hinder and larger of which fills the sac, 
while the anterior and smaller occupies the narrower neck. 
The striated appearance of this part, reference to which has 
already been made, is due, in Leydig’ s opinion, to the presence 
of a framework of connective tissue, which sends rays into or 
forms a network in it ; into this grey part there further proceeds 
a nerve, the fibres of which probably come into connexion with 
the contained cells (see PL VI. fig. 5). Ussow, as we know, 
looks upon these organs as having one of two functions, but j 
never both ; Leydig looks at the matter a little differently ; 
without affirming that they are one or the other, he says that 
whatever they are in Chauliodus , to which form Ussow ascribes 
‘ accessory eyes,’ that also must they be in Gonostoma, where the 
Russian naturalist finds ‘ glands ; ’ between the two sets there 
is, in fine, no essential difference. 
* Ussow, M., Ueber den Bau der sogenannten augenahnlichen Flecken 
einiger Enoch enfische. Bull. Soc., Moscow, liv. 1879. Pp. 79-115, 4 Pis. 
Levdig, F., Bit augeniihnliche Organs der Fische. Bonn, 1881. Pp. 100, 
10 Pis. 
