SEA-FISHERIES LABORATORY. 



105 



mammal. Text-fig". 5 represents the histology of the 

 corneal region in the normal and abnormal eyes of this 

 stickleback. 



In such a fish as this the structures in the 

 neighbourhood of the corneal region of the eye are as 

 follows (from without inwards): — (1) The conjunctiva 

 composed of an outer limiting" membrane, or cuticle, a 

 stratum of epithelium from about two to six cells deep, 

 and an inner limiting membrane. The cells are rounded 



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67 



Fig. 5. (1) The normal corneo-sclerotic junction ; (2) The normal cornea 

 over the oentral part of the lens ; (3) The abnormal cornea at the marginal 

 part of the pupil. The numbers 1-6 in the three figures refer to layers 

 which are continuous over the bulbus oculi within the limits indicated. 



or polygonal, horny, and show no evident tendency to 

 become squamous. (2) The cornea proper, which consists 

 of a rather close layer of thick, transparent, elastic fibres, 

 running in a sliglitly convoluted direction, and bounded 

 internally by a very thin limiting membrane. (3) The 

 sclerotic. This is partly cartilaginous in a Teleostean 

 fish. The cartilaginous part ceases at the corneo-sclerotic 

 junction (fig. 1), and the remaining layer (4) consists 

 of clastic fibres vrhicB lie mainly external to the 



