1915] MacCallum: Ectoparasitic Trematodes 401 



along the left side of the abdomen to empty into a rather large 

 irregularly shaped vesicular seminalis situated opposite the base 

 of the cirrus. This reservoir furnishes a small tube which en- 

 ters the bulbus ejaculatorius and passes to the pointed base of 

 the cirrus which points to and sometimes overlies the genital 

 pore. The cirrus here is long and straight except near the tip 

 where it becomes curved and pointed. At its base it is provided 

 with an oval bulbus ejaculatorius quite elongated while in nearly 

 all of the other species this is round or nearly so. The base, 

 too, of the cirrus is pointed where the tube or vas deferens joins 

 it ; it then shortly widens until it suddenly narrows to the portion 

 outside of the bulbus ejaculatorius. The cirrus proper, however, 

 is of firm chitinous tissue which cannot alter in shape even dur- 

 ing conjugation, so that as it is quite prominent it shows a good 

 index of the species (Fig 134e) . The cirrus is enclosed in a sort of 

 shell or outer cover and in this instance the penis seems to be 

 armed near the tip with fine spicules, and there appear a few of 

 these spicules also near the base. It is barely possible that this 

 condition may be owing to faulty refraction, still as almost all of 

 the specimens show the same it probably is true. 



The female genitalia, as usual, consist of an ovary, oval in 

 shape, becoming pointed anteriorly and from which part arises 

 the oviduct — this is not long before it receives the duct from the 

 seminal reservoir and the vitelline ducts ; the ootype follows and 

 merges into the uterus, being surrounded here by the shell gland. 

 The uterus terminates with a somewhat flaring mouth at the 

 genital atrium. The vagina opens at the left side of the body 

 when it is looked at from the ventral side of the body. The 

 vitellaria are plentiful, extending on both sides of the body from 

 near the pharynx to near the posterior end and across the body 

 posterior to the testis. 



These worms are all ectoparasitic, living on the gills of ma- 

 rine fishes. They are not as a rule found in great numbers, 

 although there may be many more than appears since they can- 

 not be seen in situ on the gills, and they do not wash off readily 

 on account of the firm hold of the hooks. The fish as a rule 

 which are infested with them become thin and flabby, and finally 

 die, probably owing largely to the ravages of the worm when 

 in great numbers. 



