178 THE UNIVERSITY SCIENCE BULLETIN. 



corresponding in size to those of Cercaria trivolvis Cort. The other 

 group consisted of a combination of the above-named cysts in the 

 digestive gland, and a cluster of much larger cysts of a polystome 

 cercaria on the periphery of the middle part of the snail inside of 

 the shell. 



Experimental work carried on with Planorhis trivolvis infected 

 with Cercaria kansiensis at Pratt, during the summer of 1916, 

 showed that cercarise were continually emerging from snails kept 

 in wire cages suspended in the ponds at the Fish Hatchery. These 

 snails were taken from the cages each morning and confined in 

 watch glasses in the laboratory. No characteristic swarming was 

 noticed, but instead a few cercarise could be seen emerging from 

 the snails every time they were examined. 



BIBLIOGRAPHY. 



Barker, Franklin D. 1915. Parasites of the American Muskrat. Journal 

 of Parasitology, Vol. 1, No. 4. 



Braun and Luhe. 1910. Practical Parasitology. 



Gary, L. R. 1909. The Life History of Diplodiscus temporatus Stafford, 

 with Especial Reference to the Development of the Parthenogenetic 

 eggs. Zool. .Jahrb. abt. f. Anat. u. Ont., 28:595-659. 



GoRT, W. W. 1915. Some North American Larval Trematodes. 111. Biol. 

 Monographs, Vol. 1. No. 4. 



GoLDSCHMiDT, RiCHARD. 1902. Uber Bau und Embryonalentwicklung von 

 Zoogonus mirus Lss. Centralblatt, Vol. XXXII, No. 12. 870-876. 



Kerbert, C. 1881. Beitrag zur Kenntniss der Trematoden. Archiv. fur 

 mikr. Anatomie 19, 529-579. 



VON Linstow. 1890. Ueber den Bau und die Entwicklung des Distomum 

 cylindraceum Zed. Archiv. fur mikr. Anatomie 36. 173-191. 



NicoLL, William. 1906. Some New and Little-known Trematodes. Ann. 

 & Mag. N. Hist., Ser. 7, Vol. XVII, 514-526. 



ACKNOWLEDGMENTS. 



I want to express my thanks to Dr. W. W. Cort for his kindness 

 in lending me slides, examining my preparations, and aiding in 

 the identification of species. I also wish to thank Dr. H. A. 

 Pilsbry for identifying the snails used in the studies. To Prof. 

 Bennet M. Allen, under whose direction the work has been done, 

 I wish to express my appreciation for his interest and constructive 

 criticisms. 



