162 



PLATHELMINTHES 



Family 2. MICROSTOMIDAE. 



Mouth in ventral surface near forward end ; pluirynx simple ; a pair 

 of excretory tubes present; sense pits and usually pigmented eyes pres- 

 ent: 35 species, 6 American. 



1. MiCROSTOMUM Schmidt. Preoral branch to intestine present; 

 forward end of body not proboscis-like; hinder end tapering; chains of 

 individuals formed: 15 species, in both fresh and salt water. 



M. lineare (0. F. Miiller). Body 1.8 mm. long; chain consisting of 



18 mdividuals 7 mm. long; color yellowish or pink; 2 red eyes present; 



nettle cells present which have been derived from ingested 



hydras; hinder end with a tail on which are adhesive 



papillae: eastern states; Europe. 



M. davenporti von Graff (Fig. 259). Chain consisting 

 of 4 individuals 1.5 mm. long; hinder end with numerous 

 papillae; body colorless; intestine yellow; eyes absent: 

 Long Island and Viueyard Sounds; on ulva and fucus. 



Fig. 259 



Microslomum 



davenporti 



(von Graff). 



Family 3. DALYELLIIDAE. 



Large sac-shaped pharynx present; mouth near for- 

 ward end of body; single genital pore present; ovary dis- 

 tinct from yolk glands, which are either 1 or 2 in number 

 and usually unbranched ; testes paired ; pigment eyes usually 

 present; penis usually with complex chitinous _ 



parts: about 70 species, mostly in fresh 

 water; 17 American. 



Dalyellia Fleming {Vortex Ehren- 

 berg). Body rounded in front and tapering to a point 

 behind; body not pigmented but often colored by zoochlo- 

 rellae; 2 black eyes present, near which and the forward 

 end is the mouth; genital pore in posterior third of body: 

 46 species, 13 American, all in fresh w^ater. 



D. armigera (Schmidt). Length 1 mm.; penis with 2 

 short chitinous rods, each of which has a spinose terminal 

 branch: central and eastern states; common; Europe. 



D. dodgei von Graff (Fig. 260). Penis with chitinous 

 parts of unequal size and shape forming a transverse row 

 fastened to a basal piece; length 1 mm.: the commonest 

 species; eastern states; in fresh and brackish water. 



Family 4. TYPHLOPLANIDAE. 



Pig. 260 



DahieUia 



dodgei 



(von Graff). 



1, mouth 



2, pharynx 



3, intestine 

 4, genital pore 



5, egg. 



Pharynx rosette-shaped, springing from the ventral wall of the 

 intestine and perpendicular to the ventral body surface; ovary distinct 



