The histological structure of the vitellaria is not of special in- 

 terest. We shall note that each vitelline follicle is delineated from the 

 parenchyma by a special nnembrane and contains usually a small number 

 of vitelline cells. As regards the vitelline ducts, they usually have ciliated 

 epithelia and are equipped with a well -developed musculature which is 

 represented predominantly by circular fibers (Fig. 100). Both help in the 

 rapid transfer of the vitelline cells to the oviduct. 



■.©C£) 



0.1mm 



Fig. 100. Polystoma integerrimum Froelich, sagittal section through the 

 vitelline duct. 



h .^==^:^ C 



Fig. 101. Diagram of the location of the vaginal ducts among different 

 genera of monogenetic trematodes: A--Dactylogyrus ; B --Tetrancistrum; 

 C--Murraytrema; D- -Calicotyle, Merizcotyle; E- -Pseudocotyle ; 

 F--Tristoma; Capsala; G--Polystoma; H- -Sphyranura; I--Rajonchocotyle; 

 J--Chimaericola; (According to Brinkman, 1952) K- -Diclidophoropsis; 

 Li- -Heteronchocotyle , Squalonchocotyle. (After Brinkmann, 195Z). 



64 



