LARVAL TUK.ALVTODKS FUOM FRESH-WATER I^NAILS 117 



Oral sucker ()\m\s into sinj^le mediaii rhabdocoel pouch. 



Tlir(?e pairs of salivary nnuiii <^laiids empb' i"^^^ ^^"' 

 terior re<i:ioii of pouch. 



Acetahiilum in posiciior two-hfrlis of body, considerably 

 smaller than oral sncker. 



Mass of lari>e germ cells in posterior part of body. 



l^rain mass around posterior region of digestive pouch, 

 with paired brain ganglion masses, and prominent 

 ventral trunks running cysbolad, ending anterior to 

 acetabulum. 



Median single portion of tail with prominent longitu- 

 dinal muscles. 



B. — Study of slides labelled Cercaria frondosei. 



Ampistome larva. Redia-produced. 



Body length, 405 m. ; width, 310 m. ; 

 Tail, 430 m. long by 57 m. in diameter. 



Larva heavily muscular, filled vvith mass of cystogenous 

 granules. 



Oral sucker, 06 m. in diameter, posterior sucker, 95 m. 



Bicorniate excretory bladder with small dorsal pore. 



Lateral excretory trunks dilated with large granules. 



One branch of the trunks runs forward outside the eye- 

 spots. 



Cross branch just behind eye-spots. 



Eye-spots two, distinct, surrounded by frondose arrange- 

 ment of pigment. 



Small group of germ cells immediately posterior to 

 transverse excretory canal. 



Caudal excretory trunk opens externally on right and 

 left, near distal end. 



