511] LARVAL TREMATODES—CORT 65 



D. Amphistome cercariae 



Ventral sucker at the posterior end of the body. Ex. Cercaria 

 inhabilis Cort 



E. Distome cercariae 



Ventral sucker some distance in front of the posterior end of the 

 body. 



1. Cystocercous cercariae 



Base of the tail forms a space into which the body can 

 be drawn. Ex. Cercaria macrocerca Filippi. 



2. Rhopalocercous cercariae 



Tail having as great or greater width than the body. Ex. 

 Cercaria isopori Looss. 



3. Leptocercous cercariae 



Tail straight, slender, and narrower than the body. 



a. Gymnocephalous cercariae 



Anterior end rounded, without stylet or boring spine. 

 Ex. Cercaria megalura, Cort. 



b. Echinostome cercariae 



Anterior end with a collar and crown of spines. Ex. 

 Cercaria trivolvis Cort 



c. Xiphidiocercariae 



Anterior end with stylet. Ex. Cercaria isocotylea Cort. 



4. Trichocercous cercariae 



Tail set with spines. Ex. Cercaria setifera Moulinie. 



5. Furcocereous cercariae 



Tail forked at its end. Ex. Cercaria douthitti Cort. 



6. Microcercous cercariae 



Tail stumpy. Ex. Cercaria brachyura Lespes. 



7. Cercariaeae 



Tail entirely undeveloped. Ex. Leucochloridium para- 

 doxum Carus. 



8. Rattenkonigcercariae 



Cercariae with tails joined, forming a sort of colony. 



In the present state of our knowledge it seems to me that for the 

 comparison of forms, no general grouping can be suggested which 

 will be of more help to workers. It must be recognized, however, that 

 many of the groups are purely artificial.. The Gymnocephalous cercariae 

 have little in common but negative characters, and the stylet cercariae 

 form a very heterogeneous mass. These and other groups are merely 

 temporary arrangements for convenience and must be split up or rear- 

 ranged into more natural groups as soon as our knowledge permits. 



