TURBELLARIA. 



163 



B. Dendroccelida. Larger, flatter forms with branched intestine. 



(i) Tricladida. Elongated flat " Planarians " ; the mouth 

 and tubular pharynx lie behind the middle of the body ; 

 intestine with three main branches, themselves branched ; 

 two ovaries, numerous yolk glands and testes, a common 

 genital aperture. , e.g.^ Planaria and Dendroccelum (in 

 fresh water), the former sometimes divides transversely; 

 Giinda segnientata (marine) showing hints of hite7'nal 

 segmentation ; Geodesunis and Bipaliiim (in damp earth). 



Fig. 50. — Diagrammatic figure 

 of a simple Turbellarian. 



nt. Mouth ; ph, pharynx ; ^^, digestive 

 part of gut; l.e^ longitudinal excre- 

 tory'' vessels; c.p, excretory pore; 

 Ect^ ciliated Ectoderm ; Ms, meso- 

 derm ; End, endoderm. 



Fig. 5 1 -—Diagrammatic expres- 

 sion of part of the structure of 

 a simple Turbellarian. 



Ect^ Ciliated ectoderm ; c.g^ cerebra 

 ganglion ; /.//, lateral nerve ; T-, 

 teste'^ ; 02'^ o\-arj-. 



2) Polycladida. Large leaf - like marine " Planarians," 

 with numerous intestinal branches diverging from a central 

 stomach ; with numerous ovaries and testes, without yolk 

 glands, mostly with two genital apertures. 



.g., Cycloporus (showing beginning of anus), Leptoplaiia. 

 Thysanozoon. 



