TUEBELLARIA 



163 



from yolk glands ; testes paired ; rhabdites usually prominent : 60 species, 

 all except one in fresh water, 8 American. 



1. TYPHLOPLANA Ehrenberg. Excretory ducts open with the mouth 

 into a common space, which opens to the outside; without genital 

 atrium; dermal rhabdites absent; testes very small, near the pharynx; 

 eyes absent: 2 species. 



T. viridata (Abildgaard). Body 1 mm. long, tapering at both ends, 

 behind to a blunt point, colorless, but usually colored green by zoochlo- 

 rellae; pharynx near middle of body with the genital pore behind it: 

 eastern states; Europe. 



2. CASTRADA Schmidt. Excretory ducts open as in Typhloplana; 

 with genital atrium; eyes usually absent; dermal rhabdites absent: 27 

 species, in fresh water, 1 American. 



C. hofmanni Braun. Body 1.5 mm. long, cylindrical, rounded in 

 front, tapering to a blunt point behind; pharynx somewhat in front of 

 middle of body and just in front of genital pore: eastern states; Europe; 

 abundant. 



3. MESOSTOMA Ehrenberg. Excretory ducts open as in Typhlo- 

 plana; rhabdites very prominent; testes dorsal or lateral to the yolk 



glands; genital pore in hinder third of body; mouth near 

 the middle; 2 eyes present; zoochlorellae absent: 13 

 species, 2 American. 



M. ehrenbergi (Focke) (M. wardii Woodworth) (Fig. 

 261). Body flat, up to 15 mm. long and 4 mm. wide, but 

 usually much less, tapering to both ends; forward end 

 blunt, hinder end pointed: central states; Europe; vivip- 

 f-2 arous. 



FAMILY 5. POLYCYSTIDIDAE. 



Fig. 261 



Mesostoma 



ehrenbergi 



(Woodworth). 



1, mouth 

 2, intestine. 



Two ovaries, yolk glands, and testes present; forward 

 end forms muscular retractile proboscis; rosette-shaped 

 pharynx forward of the middle of body; but 1 genital 

 pore: 16 species, 2 American. 



PHONORHYNCHUS von Graff. Male genital canal 

 with a poisonous spine: 2 species. 

 P. helgolandicus (Metschnikoff). Length 1.7 mm.: Long Island and 

 Vineyard Sounds to the Arctic Ocean; Europe; common. 



FAMILY 6. GYKATEICIDAE. 



Ovaries, yolk glands, and a single testis present; forward end forms 

 a retractile proboscis; mouth with a rosette-shaped pharynx near 

 middle of body ; genital pores separate, in hinder part of body : 1 genus. 



