338 FRESH-WATER BIOLOGY 



23 (22) Without eyes Microstomum caudatum Leidy. 



Length 1.5 to 3 mm. Commonly in chains of 2 to 8 zooids. 

 Nematocysts in place of rhabdites. Color of integument white, in- 

 testine yellow. Ciliated pits directly dorsal to mouth. Pre-oral 

 portion of intestine short. Anterior end bluntly rounded. Poste- 

 rior end narrower, bluntly pointed, tail-like, elevated. In standing 

 water and small brooks, Monroe Co., N. Y.; near Philadelphia, and 

 in West Twin Lake, Charlevoix, Mich. 



FlG. 599. Microstomum caudatum. b, brain; ph, pharynx; cp, ciliated 

 pit. (After Silliman.) 



Pharynx opens into anterior end of the intestine, which has short 



lateral diverticula Subfamily MACROSTOMINAE. 



Only one genus Macrostomum . . 25 



25 (26) Chitinous portion of copula tory organ a broad straight funnel with 

 the slender point bent at a right angle or nearly so and 

 bearing on its convex side the small opening. Vesicula 

 seminalis and vesicula granulorum connected by a narrow 

 tube. . Macrostomum appendiculatum (0. Fabricius) 1826. 



This is the form known as M. hystrix Oersted 

 1843. Length 2 mm. Unpigmented, transparent. 

 Body flattened especially at the ends. The spatulate 

 posterior end set with adhesive papillae. Rhabdoids 

 and long sensory hairs conspicuous. Two eyes, 

 black. Protonephridial tubes open on median dorsal 

 side back of the slit-like mouth. Testes and ovary 

 both paired. Asexual reproduction not known. In 

 running and standing water. Monroe Co., N. Y. ; Lin- 

 coln, Neb. 



FIG. 600. Macrostomum appendiculatum. (A) Entire 

 worm: b, brain; e, eye; ph, pharynx; di, diverticulum of 

 intestine; , intestine; te, testes; vd, vas deferens; ng, 

 ductus seminalis; vs, seminal vesicle; vg, vesicula granu- 

 lorum; ch, chitinous spicule of cirrus; $ and Q > m ale 

 and female genital pores; ov, ovary. X 35- (After von Graff.) 

 (B) Chitinous spicule enlarged. X 350. (After Luther.) 



