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what is the greatest difficulty of all, the ‘ pupil/ the ‘ lens/ 
and the ‘ vitreous body ’ are not turned upwards to the light, 
but so long as the fish is swimming they look downwards into 
the deep ; and in the case of Chauliodus are developed also on 
the membrane that lines the cavity of the mouth. 
Af l;er this piece of destructive criticism, it remains for Prof. 
Leydig to make some suggestion as to what the organs in ques- 
tion can best be compared with. He is of opinion that they bear 
the closest resemblance to the electric or ‘ pseudoelectric ’ organs 
of other fishes, and he brings many points to strengthen his 
position. Before we come to any judgment on the matter our- 
selves, it will be necessary to recall to mind the general struc- 
ture of an electric organ. These, however much they may 
vary in details and in their position on the fish that possesses 
them, always present the following points, — they are richly 
supplied with nerves, they are surrounded by a layer of 
connective tissue, which gives rise to a number of ‘ alveolar ’ 
chambers filled with a gelatinous substance. In such a form as 
the Electric Eel ( Gymnotus ), we find that on the face of each 
partition which looks backwards, there is a thin homogeneous 
layer, which is apparently formed of mucous tissue, and on the 
opposite face, or that which looks forwards, there is a much 
thicker layer. The nerves passing to and breaking up in this 
plate, give rise to the electric organ. 
When this account is compared with the description that 
has already been given of the mother-of-pearl organ, we see at 
once a very considerable resemblance ; in both there is a con- 
tained mass of gelatinous tissue, in both the same network of 
connective tissue, and in both nerve-fibres of very much the 
same character. Nor is this all ; in some species, e.g ., Scopelas 
it issoi, there is a spindle-shaped cord or plate, which is formed 
of extremely delicate granules, and this the author is inclined 
to regard as comparable to the special electric plate. With these 
essential resemblances, the form is a point of very secondary 
importance ; but even with regard to it Prof. Leydig is ready 
with an explanation. The rounded form of the mother-of- 
pearl organs is due to their position on the surface of the body ; 
like the electric organs they would probably become angulated, 
if they were massed together to form a single body. 
Whether they really have the power of developing electri- 
city is a problem that cannot yet be solved ; but the question 
has been put, and it becomes the duty of such naturalists as 
may have the opportunity to do their best to resolve it. 
Nor are we yet in a position to speak dogmatically as to 
their functions as illuminating organs ; no definite phosphores- 
cent organ has ever yet been examined which presented any 
