306 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



Fig. 3, pi. IX represents a nearly meridional section 

 of the wall of the bulbus oculi. Apart from the shape 

 of the bulbns, and the presence of the processus falci- 

 formis and campanula, the fish eye does not differ greatly 

 from that of higher Vertebrates. In the wall, however, 

 we find a choroid layer possessing features solely piscine, 

 and also the peculiar argenteal layer. The sclerotic 

 consists of two layers, (1) a layer of cartilage, ceasing 

 some distance behind the iris : on the internal surface of 

 this is the argentea; and (2) a fibrous layer which lies 

 external to the cartilaginous layer. This feature is, of 

 course, paralleled among other Yertebrata. 



The intrusive cysts lie within the thickness of the 

 cartilaginous layer of the sclerotic. This latter is, of 

 course, quite thin in the normal eye, whereas in the 

 diseased specimen the cysts are sometimes over 2 mm. 

 in diameter. The multiplication of the Myxosporidian 

 within the cartilaginous sclerotic has, therefore, distended 

 the latter layer. In section a layer of cartilage, some- 

 times, hcwever, very thin, can be traced all round the 

 cyst. In other parts of the section the cartilage thins 

 out and almost disappears, being either mechanically 

 stretched or, perhaps, reduced by the reaction of the 

 Myxosporidian tissues. The other parts of the eye were 

 apparently quite normal. The function of the organ had 

 not apparently been affected; though it is probable that 

 a kind of cataract might easily be induced by the invasion 

 of the cornea by the cyst masses. This process has 

 indeed begun in the eye figured. J. J. 



