314 



PLAT YHELMIN TILES . 



yolk glands are not separate. Convoluta Oerst. C. yaradoxa Oerst., North 



Sea, Baltic. ScMzoprora O. S. 



Fam. Prostomidae. The mouth, which is situate on the ventral surface, leads 



into a muscular pharynx. At the anterior end there is a protrusible tactile 



proboscis furnished with papillre. Prortomum Oerst. (Gyrator Ehrbg.), P. 



lineare Oerst. With pointed penial spine at the posterior end, imperfectly 



hermaphrodite, living principally in fresh water. Pr. lielgolandicum, Kef., 



completely hermaphrodite. 



Fam. Microstomidae. Ithaldoccela with separate sexes. The small but very 



extensible mouth lies near the anterior end of the body. There are laterally 



placed ciliated pits near the 

 anterior end of the body. 

 Formation of metameres 

 and transverse fission fre- 

 quently occur. Microsto- 

 iu um lineare Oerst. (fig. 



248). 

 f\ 



(2) 'Sub-order: Den- 

 drocoela. The body is 

 broad and flat, and the 

 lateral margins are often 

 plicated. There are ten- 

 tacle-like processes at 

 the anterior end. There 

 is a branched alimentary 

 canal and a muscular 

 pharynx which is usu- 

 ally protrusible. They 

 are, as a rule, herma- 

 phrodite. 



The Dendroccda are 

 mostly marine, but also 

 live in fresh water and 

 on land. In their ex- 

 ternal appearance they 

 resemble the Trema- 

 todes, and the branching 

 of their straight or 

 forked intestine is a 

 character common to the larger species of the latter. Compared 

 with the Rhabdoccda, they are distinguished by the greater develop- 

 ment of their bi-lobed cerebral ganglion, as well as by the greater 

 number of their eyes (fig. 250). The rows of papillae, or the 

 tentacle-like' processes at the anterior end of the body have 



FIG. 250. Anatomy of Poll/cells pallida (after Quatre- 

 fages). G, Cerebral ganglion with the nerves given 

 off from it ; O, mouth ; D, branches of intestine ; Ov> 

 ova; Od, oviduct; F, vagina; W.Goe, female gene- 

 rative opening; T, testes; ZI.Goe, male generative 

 opening. 



