RECAPITULATION. 505 



skin. But in the young when it is first hatched the eyes 

 are well developed. 



TyphlogobuLS californiensis is a species of Goby living 

 on the shore near San Diego in California. It lives usually 

 in the holes of a burrowing carideoid crustacean, and has 

 aborted eyes and a pink colour. The whole frontal region 

 of the skull of this fish is much modified, the scales have 

 entirely disappeared, and the spinous dorsal fin has been 

 much diminished in size. In a small specimen "9 in. long 

 the eyes were visible and apparently functional, but in larger 

 and adult specimens there is a thick layer of skin over the 

 eyes so that the latter can scarcely be perceived, and 

 certainly cannot enable the fish to see. The size of the eye 

 was not however found to be obviously different in the 

 smallest and largest specimens. 



A detailed description of the minute structure of the 

 eyes of this blind fish in the adult condition has been 

 published by W. E. Ritter in America, but unfortunately 

 he had no embryos or larval stages and therefore was 

 unable to compare the condition of the eyes in the earlier 

 and later stages of life or of the ontogeny. The smallest 

 specimens examined were 19 mm. long or nearly 4 in. and 

 the largest 63 mm. or nearly 2f in. Comparison of the 

 various specimens did not prove either a constant advance 

 or a constant retrogression in the development of the eye 

 between these sizes, but it is noteworthy that the only 

 specimen in which the lens was entirely absent was one of 

 the maximum size, 63 mm. in length. The usual condition 

 of the eyes was the following. The epidermis over the eye 

 is similar to the ordinary epiderrnis. Beneath this is dermal 

 fibrous tissue also of the ordinary kind. xAround the eye is 

 a thin layer of denser tissue representing the sclerotic and 

 cornea. The choroid is thin and rudimentary, in front of it 

 is the pigment layer of the retina which is proportionally 

 very thick and contains no cellular elements. In front of 

 the pigmented layer is the cellular part of the retina which 

 is but little differentiated ; it contains however a layer of 

 rods but no cones. The lens is present with the exception 

 mentioned above, but the argentea is entirely absent, and 



