75] LIFE HISTOR Y OF TREMA TODES—FA UST 75 



acetabulum. No glands occur in the pharynx or cecal regions, but in the 

 prepharynx region, just within the oral aperture, is a band of about fifty gob- 

 let cells of a glandular nature. The salivary-mucin glands are found at the 

 sides of the acetabulum. They consist of eight cells for each group. They 

 are relatively large, vesicular, and have common ducts opening into the oral 

 pocket. In addition to the usual transverse and longitudinal systems just 

 within the integument (Fig. 97, 98), large muscle elements are scattered 

 thruout the parenchyma. 



The genital organs (Fig. 96) consist of a prominent vagina, a well-defined 

 Laurer's canal, and a group of massed organs in the vicinity of the ootype. 

 In addition, there are the yolk follicles, distributed over a wide range of the 

 dorsal side of the animal. The follicles are closely massed together. This 

 species suggests a Plagiorchid genital system. 



Cercaria racemosa Faust 1917 



Cercaria racemosa belongs to that group of stylet cercariae usually desig- 

 nated as cercariae ornatae, by virtue of their possession of a fin-fold structure 

 to the tail. While this separation may be concomitant with a deeper, more 

 fundamental difference of type, it is well to bear in mind that fin-folds occur 

 in other groups, such as in monostomes, Cercaria lophocerca (Fihppi, 1857:5; 

 Fig. 3), echinostomes, Cercaria echinatoides Fil. (La Valette:1855,Taf. I, C), 

 and among the furcocercous larvae, Cercaria cristata (La Valette, 1855,Taf. 

 II, K). It may be looked on as a modification of the caudal organ for swim- 

 ming. 



The body of Cercaria racemosa is elongate ovoid, measuring 0.29 mm. in 

 length by 0.11 mm. in width (Fig. 100). It is characteristically broadest 

 just ahead of the acetabulum. The tail consists of a central lanceolate region 

 and a lateral ruffled fringe, which is most conspicuous at the distal end. The 

 tail measures 0.22 mm. in length and 0.04 mm. in width at the base. It is 

 inserted into the posterior extremity of the trunk, altho there are no lateral 

 sinuses to be found in this caudal pocket. The acetabulum is sHghtly caudal 

 to the middle of the body. It measures 26/i in diameter, while the larger oral 

 sucker has a diameter of 36iu. The stylet organ (Figs. 101, 102) is delicately 

 attenuate, with a reinforced tip. It is 27/i long and about 5^ wide at the base. 



The species was found in the liver of Lymnaea proxima in the chara sloughs 

 of the Bitter Root River at Fort Missoula, Montana, in October 1916. It 

 occurred as a minor infection along with C. dendritica and C. gracillima. The 

 parthenita is an irregular polygonal sporocyst about 0.62 mm. long and 0.38 

 mm. thick (Figs. 104, 105). At one end is situated a pocket of glandular 

 cells which attach the sporocyst to the host. This is done by the exudation 

 of a mucus. It is doubtful if these cells are at all muscular. At the antipodal 

 end is the germinal epithehum, from which germ balls arise. Only a few 

 cercariae develop within the sporocyst at any one time. 



The bladder of the excretory system is truncate, with a common median 

 vessel leading into it from the anterior end. Lining the vesicle at the anterior 



