BLINBXESS IX MARIXE FISHES. 635 



Tlie several subjects deseiilied hereinnfter were received by 

 the writer from tlie Superintendent of the Brighton Marine 

 Ar|ua.rium, Mr. E. W. Cowley, to whom thanks are due. 

 Acknowledgment of much assistance in the preparation of thi.s 

 paper is a,lso accorded to Mr. John Hopkinson and to the late 

 Mr. G. Harold Drew. 



Hofer* traces the progress of the more usual foi-m of blindness 

 in freshwater fishes in the following manner : (a) Corneal 

 "cataract" due to injury or pathogenic bacteria attacking the 

 integument ; (/3) gradual necrosis of the cornea-epithel and 

 outer surface of the cornea; (y) perforation of the cornea. 

 Complications which may occur are " Keratoglobus " in the 

 earlier stages, and Saprophytic growth attendant upon the 

 bacterial lesions. 



In the case of several freshwater fishes, the same author 

 describes a not uncommon form of blindness due to parasites 

 {Diplostomum larvae), but of all the marine fishes which herein 

 receive notice, none has been aifected in this manner. More- 

 over, it may be recorded that no evidence of Saprophytic growth 

 occurred on even the woi-st examples t. 



1. Traumatic Corneal Opacitis in a Conger Eel 

 (Conger vulgaris). 



The subject of this note was a Conger Eel which measured 

 .3 feet 7 inches. It had lived in the Aquarium for nearly six 

 years, retaining complete health until November 1912, when, 

 accoi'ding to the Superintendent of the Aquarium, Mr. E. W. 

 Cowley, it went completely blind within the space of a week. 

 It was destroyed immediately, when, from an observation of its 

 behaviour, both eyes appeared to have become wholly useless. 



An examination of the head of this specimen showed that the 

 right cornea-epithel was perforated in two places and the left in 

 five, each perforation being just large enough to admit a seeker 

 •5 mm. in diameter. Extensive peneti-ation of sea- water followed 

 probably by bacterial lesions had occurred throughout the under 

 surface of the cornea-epithel, those on the left side extending to 

 the adjacent epidermis of the gill-covers, destroying the colour- 

 cells, and rendering the part affected opaque white. The eye 

 itself, when superficially examined, was so completely dimmed 

 as to render observation of the characteristic yellow iris difiicult, 

 except in strong light. 



The term " corneal opacitis " would be somewhat loosely 

 applied in this instance, since upon removal of the integument 

 the cornea pi-oper was found to be completely free fiom injury, 

 and but slightly affected with opacitis. 



* Op. clt. p. 291 etc. 



f For a deteviiiination of tliis fact the writer's thanks are due to Miss Lorraine 

 Smith, of the British Museum. 



