90 BULLETIN OF THE 



meats the former ; and this may have become neccssar}'^ from the peculiar 

 )node 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 ver}' 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 crises 

 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 exce[)ting in the chorio-caj)illaris, 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- 



