60 BULLETIN OF THE 



section, while the measurements in the case of the first three were made 

 with the eyes in place in the head, the head having been cleared in 

 clove oil. It is undoubtedly true, that some of the difference in size 

 between the last mentioned eye and the first three was due to shrinkage 

 in it during its passage through the paraffine. I have made numerous 

 measurements of the same eyes before embedding and after cutting, and 

 have always found the sections somewhat less in diameter than the 

 whole eyes, even when all precautions had been taken to prevent shrink- 

 age. But certainly shrinkage cannot account for the great difference 

 found here between the eye measured in section, and the one of an in- 

 dividual of the same length measured in the head. This small eye, I 

 should add, was the only one that I have found in which the lens was 

 wholly absent. This eye will be described later on. In a specimen 

 25 mm. long the axial diameter of the eye was 0.28 mm., and its equa- 

 torial diameter was 0.45 mm. In a specimen 19 mm. long the diameter 

 in the long axis of the head was 0.28 mm., and transverse to this it was 

 0.39 mm. It appears from these measurements that the eye does in- 

 crease somewhat with the increase in size of the animal, though it is 

 true that, in view of the obvious individual variation in size in specimens 

 of nearly the same length, not enough of the smaller specimens have 

 been studied to determine definitely how much this increase amounts to. 

 A sclerotic coat, well defined from the surrounding connective tissue, 

 is always present, though in some places its fibres, both singly and in 

 bundles, leave their concentric course and pass off into the connective 

 tissue, and thus bring about an intimate connection between the two. 

 In some places the connective-tissue fibres not belonging to the sclera, 

 but in its vicinity, are seen to have taken on a concentric direction even 

 at a considerable distance from the eye, and to have become more 

 numerous and more closely packed than is the case with the subcuta- 

 neous connective tissue in general. There is thus brought about a 

 fusion to some extent of the eye bulb with the tissue in which it is 

 embedded. This statement applies especially to the eye the section of 

 which is shown in Figure 6. In most sections numerous flattened con- 

 nective-tissue cells are found in the sclera ; and in all the eyes that I 

 have sectioned the sclera is cai'tilaginous in the region corresponding to 

 the ora serrata of the retina. The cartilaginous layer is usually only 

 one cell thick, but occasionally it is two or more cells thick (Figs. 5, 6, 

 and 12). In many specimens the cartilage does not extend entirely 

 around the eye in the equatorial zone, and in no case have I seen it 

 extend more than half-way back to the entrance of the optic nerve. No 



