General Ecology 23 



tailed studies on the stages in fresh-water snails. Many other works might 

 he quoted but a sufficient number have been indicated to show the role 

 played by the fresh- water snails, particularly the Planorbidae, in the life 

 cycle of the trematode worms. Some additional titles are listed in the 

 bibliographies accomj)anying the papers mentioned in this chapter. 



During the anatomical investigations made for this work careful note 

 was made of the presence of larvae of trematode worms, principally 

 cercariae and a few rediae. Over a thousand specimens of mollusks were 

 examined but only a few contained parasitic worms. The following species, 

 arranged under subfamilies, were observed to be infested. 



Subfamily Planorbinae 



No -spocimens of this subfamily were found with cercariae or rediae. 

 Subfamily Segmentininae 



Scgmentina nitida from marshes in a meadow in Czneriakow, a suburb of Warsaw, 

 Poland. Sent bj' Mr. A. Jankowski. Cercariae were abundant,- mainly in the ovotestis 

 which was almost destroj^ed. All specimens examined were infested. 



Drepanutremn hoffmani from pond near Isabela, Puerto Rico. Sent by Dr. Wil- 

 liam A. Hoffman. Heavily infested with stylet cercariae. 



Austmlorbi.fi glahratus from near San Juan, Puerto Rico. Sent by Dr. Hoffman. 

 Various degrees of infestation. 

 Subfamily Helisomatinae 



Helisomn anceps, from Unionville. Connecticut. Collected by F. C. Baker. One 

 specimen with lung ca\ity filled with rediae and one specimen with cercariae in liver 

 and genitalia. 



Helisoma trivolvis lentum, from near Urbana, Peoria, and St. Joseph, Illinois. 

 Cercariae in liver and ovotestis. 



Helisoma subcrenatum from Cottonwood Pass, near Gypsum, Colorado. Sent by 

 Junius Henderson. Four out of six specimens with cercariae in different parts of the 

 body, mostly the li\'er. Some specimens from a sluggish creek one mile west of Devon, 

 Montana, collected by J. Henderson and Hugo Rodeck, contained cercariae, mostly in 

 the liver. 



Helisoma plexatum, from Teton River, north of Rexburg, Idaho, collected by 

 J. Henderson; one out of six infected. 



Helisoma hornii, from Paul Lake, Kamloops District, British Columbia. Sent by 

 Dr. D. S. Rawson, Uni^•ersity of Saskatchewan. About one-third were affected by 

 cercariae. 



Helisoma pilsbryi from Chetek Lake, Barron Co., Wisconsin. Collected by 

 F. C. Baker. Cercariae in eight specimens with the liver and ovote.stis mo.stly 

 affected.. 



Helisoma corpulentum from Miles Bay, Lake of the Woods, Canada, Fall Lake, 

 Ontario, Canada, and Knife Lake, St. Louis Co., Minnesota. Collected by Dr. 

 A. R. Cahn. Many infested with cercariae. 



Heli^soma eorpulcntum multicostatum, from Lake Kahnipiminanikok, Ontario, 

 Canada. Collected by Dr. A. R. Cahn. One out of six with cercariae. 



H(lisoma ivhiteavesi from Kashabowie Lake, Ontario, Canada. Collected by 

 Dr. Cahn. One out of four infested with cercariae. 



Helisoma campanulatum wisconsinense from Pirate Island, Lake Nipissing, On- 

 tario, Canada. From the Biological Boaixi of Canada. One out of five specimens with 

 cercariae. 



Subfamily Planorbulinae 



Menelus cooperi callioglyptus from Quatana, Vancouver Island, British Co- 

 lumbia. Received from Dr. W. A. Clemens. Two-thirds of the specimens examined 

 (about a dozen) were infested with cercariae, in several examples almost consuming 

 the liver, albumen gland, and ovotestis. In several specimens the cercariae were 

 most numerous about the stomach. Several hundred were observed in some siJecimens. 



Ml 111 tux cooperi from small lakes on Mt. Con.stitution, Orcas Island, Puget 

 Sound, Washington. Collected by Dr. Dale Foster. Of fifteen specimens examined, 

 one contained cercariae. 



Meuetas dilutatus from L'nionville, Connecticut, fourteen miles west of Hartford. 

 Collected by F. C. Baker. One specimen in sixteen contained cercariae. 



