638 ox BLIXDNESS IX MARIXE FISHES. 



a slight increase on the anterior margin, the total extent, how- 

 ever, being slightly less than that observed in the transverse 

 sections, amounting i-oxighly to slightly less than half the diameter 

 in affected tissue. The term " cortical cataract,'"' as applied to 

 the human subject, would perhaps aptly describe the condition 

 observed when in its earlier stages*. 



The behaviour of these fish in the Aquarium is a matter 

 deserving of some coniment. Habitually they were observed to 

 swim in mid-water, maintaining one position often for several 

 minutes together, and seldom exhibiting much activity in move- 

 ment. It is a somewhat remarkable fact, but one which the 

 present writer, by an observation extending over several weeks, 

 can personally vouch for, that on no occasion were any of the 

 specimens seen to come in contact with each other, the sides 

 of the tank, or the glass. Pollack with normal vision installed 

 in an adjacent tank were easily attracted Avhen a moistened 

 finger-tip was rubbed rapidly up and down the glass causing 

 vibration thereby, less freely by gentle tapping. The blind fish, 

 even when situated within a, few inches from the glass, made no 

 effort to respond to this attraction. 



When food, in the form of finely-cut fish, molluscs, etc., 

 vffis offered, it was allowed to sink to the bottom and remain 

 there for several minutes before a search after it was made. 

 This took the form of a wholly haphazard grubbing about on the 

 bottom, the fish often making a vigorous " bite " immediately 

 beside a fragment, this operation being repeated until the morsel 

 was secured. Although a sufficiency of food was placed in the 

 tank daily, and on one occasion one individual fish was observed 

 within the spa.ce of 15 minutes to secure three fragments of 

 moderate size, all the specimens when examined post-mortein were 

 found to be very ill-nourished and considerably below normal 

 weight. 



Note: — The writer is indebted to Mr. J. 0. G. Ledingham, of 

 the Lister Institute of Preventive Medicine, for the following 

 report respecting the histological condition of the lens in one of 

 the above specimens. This gentleman writes " I cut Celloidin 

 sections of the fish's eye you sent to me in formalin. They were 

 very difficult to cut owing to the fact that the lens provetl to be 

 completely calcareous. This was the only obvious lesion I could 

 detect. I saw no micro-organisms in the sections ; but, as you 

 will understand, the sections were not satisfactory for the 

 demonstration of micro-organisms." 



* Vide L. B. llarman, " Aids to Ophthalmology," p. 83. 



