APPENDIX. 353 



by a cataract ;* and another, a Hydatid? from the 

 eye of a young woman. 



Besides those that infest our own visual organs, 

 quadrupeds, birds, reptiles, and fishes, have each 

 their eye-worms. Amongst those to which the 

 will of Providence has assigned their station in 

 the eyes of the latter class of animals, is a re- 

 markable one, 3 which Dr. Nordmann discovered 

 in those of several different species of perch,* 

 sometimes, in such numbers, as must have in- 

 terfered with that distinct sight of passing objects, 

 which appears necessary to enable predaceous 

 animals to discover their prey in time to dart 

 upon it and secure it ; in a single eye the Doctor 

 detected, in different parts, 360 ! of these ani- 

 malcules : when much increased they often pro- 

 duce cataracts in the eye of the fishes they 

 infest. This little animal appears something 

 related to the Planaria, or pseudo-leach, and, to 

 judge from Dr. Nordmann's figures, seems able, 

 like it, to change its form. 5 Underneath the body, 

 at the anterior extremity, is the mouth ; and in 

 the middle are what he denominates two suck- 

 ing-cups ; 6 these are prominent, and viewed 

 laterally form a truncated cone ; the anterior 

 one is the smallest and least prominent, and 



1 F. Oculi humani. 2 Cysticercus celluloses. 



3 Diplostomum volvens, PLATE I. B. FIG. 5. 



4 Ibid. FIG. 6. 



5 See Nordmann's Micrograph, i. t. ii./, 1 9. 



6 Saugnapfe. 



VOL. I. A A 



