505] LARVAL TREMATODES—CORT 59 



and widens slightly at its anterior end. Into it flow two vessels from 

 the region of the oral sucker on each side, which are met by vessels from 

 the posterior end at the region of the acetabulum. Small branches lead 

 from the flame cells and connect with these branches. Figure 76 shows 

 the excretory system of Cercaria hemilophura. 



The anlagen of the reproductive organs are represented by a two 

 lobed mass of nuclei dorsal to the acetabulum. 



According to Liihe 's classification of the Xiphidiocercariae Cercaria 

 hemilophura would belong with the group Cercariae ornatae. He gives 

 the following definition for this group : 



' ' Distome Cercarien mit Bohrstachel, deren schlanker Ruderschwanz 

 einen Flossensaum besitzt. ' ' 



He included in this group Cercaria ornata La Valette and Cercaria 

 prima Ssinitzin. This is certainly not a natural subdivision, since the 

 three forms are very different in other structures. The presence of 

 such a character as the "Flossensaum" hardly forms the basis for a 

 natural group. Since it has been developed also in such widely different 

 groups as the monostomes and the echinostomes. At the present state 

 of our knowledge it seems impossible to relate Cercaria hemilophura 

 to any natural group. Neither is there any suggestion as to the further 

 development of this species. 



MICROCOTYLOUS CERCARIAE 



The tissue above the gills in three out of thirty-six specimens of 

 Campeloma subsolidum from Hartford, Conn., was heavily infected with 

 oval thin-walled sporocysts. The sporocysts had granular, somewhat 

 opaque walls, varied in shape from almost round to elongate oval, and 

 contained small cercariae in different stages of development. None of 

 the cercariae were fully mature and none were found free in the tissues 

 of the host. There was little movement of the cercariae either within 

 the sporocysts or when freed. I propose the name Cercaria leptacantha 

 for this species on account of the small size of the stylet. 



The sporocysts (Fig. 81) varied from 0.26 mm. to 0.41 mm. in length 

 and from 0.15 mm. to 0.26 mm. in width. 



The body of Cercaria leptacantha (Fig. 80) is oval elongate and 

 almost circular in cross-section. The average measurements of five well 

 extended mounted specimens are 0.12 mm. in length and 0.063 mm. 

 in width. The tail is not fully developed still remaining as a direct 

 continuation of the body and having little power of movement. It is 

 less than the length of the body and slender, averaging 0.081 mm. in 

 length and 0.016 mm. at its greatest width. 



