WILSON, PARASITIC COPEPODS FROM JAPAN. 13 



eye was an adult female without egg strings, the others were 

 development stages. 



This material has proved of peculiar interest for several 

 reasons. The species was originally established upon a single 

 mutilated female and nothing was known of the head and 

 first three thorax segments. 



The present specimens fulJy confirm the establishment 

 of the species and also furnish much information with refe- 

 rence to the habits and life history. In particular they tell 

 US about the mode of attachment and how the parasite gra- 

 dually assumes its peculiar form. 



Mode of attachment. The young parasite, on reaching 

 the requisite stage of development, fastens itself to the out- 

 side surface of the fish's eye. It then burrows through the 

 cornea or the sclerotic coat into the interiör of the eyeball, 

 passes along the inner wall of the latter to the retina, bur- 

 rows out through this to its outer surface and spreads its 

 flattened head out över that surface, with its mouth in con- 

 tact with the network of blood vessels which supply the 

 retina, close to the retinal artery. 



From either side of the head profusely branch§d soft 

 processes grow out över the back of the retina and hold the 

 head securely in place. At the same time the irritation 

 causes an outgrowth of the surrounding tissue of the eyeball, 

 which spreads över and between the soft processes and 

 covers the head, thus aiding its anchorage. 



The point where the parasite first enters the eye even- 

 tually comes to be opposite the fourth thorax segment in 

 consequence of the burrowing, and from this segment four 

 chitin horns grow out, which branch more or less profusely 

 and fästen themselves firmly into the wall of the eyeball. 



As would naturally be inferred, the separation of one 

 of these parasites from the eye of its höst is a very tedious 

 and difficult process, if the specimen is to be secured unin- 

 jured. 



Specific characters of adult female. Since the original 

 description was made from a mutilated specimen it seems 

 best to revise and enlarge it. Cephalothorax much longer 

 than wide, made up of the head and the first four thorax 

 segments thoroughly fused. Anterior end squarely truncated 



