THE FREE-LIVING FLATWORMS (TURBELLARIA) 



335 



12 (13) Anterior end bluntly pointed, ciliated pits about as far from end of 

 body as width of body at that point. Posterior end taper- 

 ing uniformly to a blunt point. 



Stenostomum leucops (Anton Duges) 1828. 



Length of single individuals 0.5 to 1.5 mm. Asex- 

 ual reproduction by budding 2 to 4 zooids common, 

 rarely 9 zooids. Intestine continuous through zooids. 

 Rhabdites small, numerous. Two patelliform organs 

 which consist of numerous spherical bodies. Male 

 sexual organs mature in August, female in September. 

 At this time the animal becomes large, sluggish, and 

 somewhat reddish-brown in color. The six-lobed 

 ovary lies under the intestine. The oval-shaped 

 testes which consist of many closely compacted lobes, 

 lie above the pharynx and open into the seminal 

 vesicle which leads through a short canal to the 

 opening on the dorsal surface. Abundant on plants 

 in quiet water such as small lakes or ponds. Mass., 

 N. Y., 111., Mich., Neb. 



WV 



Op 



FIG. 592. Stenostomum leucops. (A) dorsal view of anterior end: b, brain; m, mouth; k, protonephrid- 

 ium; phd, pharyngeal glands; do, patelliform organ; cp, ciliated pit. X 200. (B) Entire worm, cp, 

 ciliated pit; c, cilia; b, brain; m, mouth; ph, pharynx; in, intestine; wo, protonephridium; op, external 

 pore of protonephridium. X 100. (After Ott.) 



13 (12) Anterior end very bluntly rounded with ciliated pits very near the end. 

 Posterior end of body narrow and forming a long slender tail, 

 somewhat spatulate in shape, except where division has 

 recently taken place, in which case the tail is shorter and 

 more pointed. . . . Stenostomum speeiosum Stringer 1913. 

 Length 2.25 mm. A large rhabdocoel which moves rather slowly and very gracefully. The 

 ciliated pits are placed close to the blunt anterior end, much farther forward than in 5. leucops, 

 also are deeper and narrower than in the latter form. The mouth is about as far from the an- 

 terior end as the diameter of the body at that point, and is surrounded by glands. The pharynx 

 has delicate longitudinal striations. The intestine shows many large highly refractive color- 

 less bodies, probably fat globules. Nothing definite can be said of the light-refracting organs 

 which were difficult to identify because of the unusual size of the animal. A few specimens 

 collected from pond with S. leucops. Lincoln, Neb. 



cp 



Stenostomum speeiosum. cp, ciliated pit; b, brain; ph, pharynx; m, mouth with surrounding 

 glands; e, egg. X 45- (Original.) 



Wall of digestive tract pigmented. .,.,..., 15 



