THE EYE-LIKE SPOTS IN FISHES. 
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growth from the sides of the skull, which distinguishes the 
Tortoises, is to be found, to all appearance, in an African 
Mammal (the Rodent Lophiomys ), and a lowly Frog ( Pelobates ), 
found in Central Europe. 
Before suggesting any definite answer to the questions 
thus raised, we must say a few words about the set of organs 
to which Dr. Ussow does not ascribe any optic function, 
although he regards them as really belonging to just the same 
category. As seen in Scopehcs, they have the form of a pear- 
shaped sac, the wide end of which lies in the tissues, while the 
narrower end projects a little above the surface ; the latter, 
which is separated from the part below it by a kind of con- 
striction, contains spherical cells, while the lower portion is 
filled with cells of a polyhedral form ; but there is no central 
cavity, and there is no kind of orifice. This kind of organ the 
author looks upon as a gland, and in the more complex case of 
Maurolicus there is no doubt that in what he saw there, there 
is much to support his view. The ‘ glands ’ are elongated and 
flask-shaped, surrounded for two-thirds of their length by a 
pigmented membrane ; on the inner face of this there is a 
layer made up of white fibres, and presenting the appearance 
of a tapetum. Here, again, there is no duct to the gland. 
We come now to a species which has been examined both 
by Dr. Ussow and Prof. Ley dig — Argyropelecus hemigymnus — 
and it would be interesting, had we space, to compare what 
these two naturalists have to say about this form. This 
curious fish (PI. VI. fig. 2), which is here represented as twice 
its natural size, is found not uncommonly in the Mediterranean, 
and is remarkable for the great depth of the anterior portion 
of its body, and the wonderful way in which it narrows ofi 
quite suddenly in the region of the tail. In front of the eye 
there is one spot, and behind it there are two, and six smaller 
ones are found on the gill-membrane, and six larger ones are 
found on the throat ; by the gill-cleft we see four, the largest 
on the body, of which two lie in front and two behind the 
cleft. At the side of the body, and close to the abdominal 
profile, there are twelve, which decrease in size from before 
backwards ; and above these there is a second row of six, all 
of which are of very much the same size. Between the ventral 
and anal fins there are again four, and behind the anal fin 
there are six others, of which the smallest are in the middle. 
Just in front of the tail-fin we find the last quartet of these 
organs. This gives us fifty-three in all, and as they are paired, 
we find one hundred and six of these comparatively large spots 
on the body of this small fish. So much of our account is taken, 
as is also the illustrating figure, from the description given by 
Ley dig, who would appear to agree so far with Ussow, who 
