69] LIFE HISTOR Y OF TREMA TODES—FA UST 69 



the main lateral trunk divides into inner and outer tubes, each of which has 

 a number of branches and capillaries. The main tube of the tail is median, 

 with no prominent tubules. 



The digestive system consists of an esophagus provided with a pharynx for 

 most of its way, and, behind the pharynx, a typical gut extending to the 

 posterior plane of the acetabulum. 



The salivary-mucin glands in C. crenata are of a unique type. An outer 

 series of eight small vesicular cells, with a common duct system into the oral 

 pocket, corresponds to the usual salivary-mucin gland system of cercariae. 

 These glands are readily made out in the living worm. An inner series of 

 five cells, two of which are just behind the pharynx and three behind the ace- 

 tabulum, empty thru a common duct system into the oral pocket. This 

 series is not seen in the living larva, but in stained specimens the cells show 

 small vesicular nuclei with deeply staining cytoplasm and numerous chromo- 

 philic granules. This inner series probably consists of a type of salivary 

 gland different histologically and suggests a correspondingly different function. 



The genital cell masses are prominent and are well differentiated early in 

 development. Their structure and position are indicated in figure 59. The 

 ovary lies posterior to the acetabulum and median whereas Laurer's canal 

 lies anterior and to the left. The uterus is characterized by a double coil, 

 which ends in a moderate sized vagina, just anterior to the acetabulum. The 

 vitellaria are limited to three cords which lie in a transverse plane just 

 posterior to the ovary. The large flask-shaped testes lie behind the ovary. 

 This genital system suggests the Plagiorchiine arrangement. The distribution 

 of vitellaria is similar to that described by Poirier for Plagiorchis sauromates 

 (1886, pi. 2). 



Cercaria glandulosa Faust 1917 



A stylet cercaria characterized by a multiplicity of glands has received 

 the name of Cercaria glandulosa. It is somewhat larger than C. crenata, is 

 more oblong-ovate, and is a much more active larva (Fig. 60). The body 

 measures 0.45 mm. in length and 0.2 mm. in width. The tail is slightly 

 shorter than the body, 0.35 mm. in length, by 50/i to 60/i in section at the base. 

 The tail is set within the caudal pocket. This pocket is provided with a 

 pair of locomotor grooves, in which are set a number of stiff spines. Below 

 the insertion of the tail is a small lappet (Fig. 63), provided with three spines 

 directed posteriad. A mucoid secretion is present in the sinuses of the pocket, 

 lateral to the base of the tail. 



The stylet organ measures 39yii in length by 5m in width at the base of the 

 shank. It is reinforced all thru, but especially at the base of the shank, and 

 thruout the quill. The point of the stylet is blunt. The stylet, as well as 

 the entire body, is very delicate, and is shattered by the slightest pressure of 

 the cover slip. The oral sucker is directed downward; it measures 86^ in 

 diameter, while the acetabulum, in the middle of the ventral side, is smaller, 

 with a diameter of 66//. 



