96 BULLETIN OF THE 
ments the former ; and this may have become necessary from the peculiar 
mode of life of the animals. It is quite certain that the water of the 
small holes under stones, in which they live, would contain less aerating 
oxygen than would that of the open sea; and consequently a greater 
absorbing surface would be essential in order to effect a normal aeration 
of the blood. 
SUMMARY. 
The facts observed and the conclusions reached may be summed up 
as follows. 
The Eyes. 
1. In the smallest examples studied the eyes, though very small, are 
distinctly visible even in preserved specimens, — so distinctly that the 
lens is plainly seen. In the largest examples, on the other hand, they 
are so deeply buried in the tissue as to appear even in the living animals 
as mere black specks, while in preserved ones they are in many cases 
wholly invisible. 
- 2. Neither in small nor in large specimens does the epidermis over the 
eye differ in thickness or structure from that of adjacent regions. In 
the large individuals the much greater thickness of the tissue here is 
brought about by an increase in the sub-epidermal connective tissue, the 
growth of which can be seen taking place in the embryonal connective- 
tissue cells that are found here. 
3. As is the case with rudimentary organs generally, the eye is subject 
to great individual variation in size, form, and degree of differentiation. 
4. The only parts of the normal teleostean eye no traces of which have 
been found are the argentea, the lamina suprachoroidea, the processus 
falciformis, the cones of the retina, the vitreous body proper, the lens 
capsule, and in one specimen the lens itself. 
5. In the parts present the rudimentary condition of the organ is seen 
in the very slight development of the choroid, no cellular elements being 
present in this excepting in the chorio-capillaris, and here to a quite 
limited extent, the rest of that layer being composed exclusively of pig- 
ment; in the fact that the choroid gland is composed entirely of pig- 
ment; in the fact that the iris, though of fully the normal thickness, 
is almost entirely of pigment, there being on its outer surface in some 
specimens a small amount of cellular material, which probably represents 
the ligamentum annulare ; in the great proportional thickness of the pig- 
ment layer of the retina and the entire absence in it of anything except- 
