Sea-fisheries laboratory. 327 



optic nerve, is elongated in the longitudinal axis of the 

 body, and curves round the nerve so that its concave 

 margin faces the temporal side of the eye. It is not a 

 gland sensu stricto, but a rete mirabile. The ophthalmic 

 artery on entering the bulb immediately breaks up into a 

 number of short capillaries which run transversely to the 

 long axis of the gland ; at the lateral margin these turn 

 backwards on themselves, and open into a very prominent 

 vein which traverses the whole length of the gland. From 

 this vein a very short transverse trunk pierces the sclerotic 

 and forms outside the bulb the distal extremity of the 

 superior jugular vein. We are unaware of any plausible 

 hypothesis as to the function of this organ. 



The Retina presents no features of special interest. 

 The radiation outwards of the fibres of the optic nerve 

 towards its periphery is very striking. A prominent black 

 line runs outwards from the place of entrance of the optic 

 nerve to the temporal margin of the retina. This is the 

 choroidal fissure, which here divides the retina, and by 

 exposing the pigmented choroid beneath shews as a black 

 line. 



The Processus Falciformis and Campanula Halleri.— 

 A delicate fold of the choroid projects through the 

 choroidal fissure into the vitreous humour. This is the 

 processus falciformis. Its distal extremity is swollen out 

 into a bilobed pear-shaped enlargement — the Campanula 

 Halleri, which is attached to the lens. These structures 

 are said to form an accommodation apparatus. Accom- 

 modation in the fish eye is effected not by an alteration in 

 the curvature of the lens but by its approximation to the 

 retina through the contraction of the muscular tissue in 

 the above campanula and processus. The elasticity of the 

 suspensory ligament increases the distance between lens 

 and retina. 



