Two New Trematodes of the Family Gyrodactylidce. ^3. 



the dorsoventral muscle fibres take a course parallel to that of the 

 canal aud undoubtedly function as retractors. 



The egg shell is provided with a filament at one extremity 

 and measures 0.07 mm. by 0.04 mm. 



II. Tetrancistrum sigani, n. g., n. sp. 



This worm is common on the gills of Siganus fuscescens 

 Houttuyn, a marine food fish distributed from Tokyo southwards 

 to the Philippines. The body is flattened dorsoventrally, broad 

 at the middle and narrowed towards the ends. The front end is 

 lightly 4-lobed when moderately retracted, but can be produced 

 into as many tentacle-like processes, as in Dactylogyrus, although 

 the inner pair is not so conspicuous as in that genus. From this 

 front end the body narrows slightly for a short distance and forms 

 what may be called the neck portion, which is free of the 

 vitellarium extending through the greater part of the length of 

 the body. The caudal portion which is also free of the vitella- 

 rium is nearly as long as the neck portion and its posterior end is 

 expanded into a caudal disk, which is clearly set off from the 

 adjacent parts, transversely oval in shape and carries near the 

 centre two pairs of large hooks but lacks the marginal hooks 

 entirely, a peculiarity which distinguishes it from the closely allied 

 Ancyrocephcdus. In the brain are found irregularly scattered 

 pigment granules, some of which may be so located as to simulate 

 the four eye spots often found in allied genera. The animal is 

 colourless except for the yellowish vitellarium, which shows 

 through the transparent tissues. Specimens may be obtained at 

 all seasons of the year and the size is 1.2-2 mm. by about 

 0.5 mm. in the preserved state. Egg laying appears to take place 

 all the year round. 



The materials of this species that we have been able to obtain 

 so far are in an unsatisfactory state of preservation histologically, 

 hence we will limit ourselves to a general account of the anatomy 

 of the animal. 



The cuticle is of nearly uniform thickness in all parts of the 



