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Notes on Parasites Found in Feogs in the Vicinity of 



St. Paul, Minn. 



By H. L. Osborn. 



(Abstract.) 



Our knowledge of the parasites of even the commonest animals is very 

 incomplete. Examinations of all the organs and at all seasons of the year 

 and- extended over a period of several years have never been made except, 

 possibly, for a few of the domesticated animals where the information 

 possessed an evident and immediate utilitarian bearing. Such studies of a 

 number of common and abundant animals are much to be desired. If a 

 body of such information were available it would be of great service to 

 students of the trematodes and very likely make it possible to complete 

 many life histories, only fragments of which are known at the present 

 time. The present paper is a first step in an attempt to do this with refer- 

 ence to the common frogs in the neighborhood of St. Paul. Twenty-one 

 frogs were examined in June, seven in September and nine in November. 

 These numbers are found to be too small for anything but a preliminary 

 survey of the ground and larger numbers will be examined next year. 

 The walls of the ccelom, particularly in the dorsal and anterior regions, 

 are infected by nearly mature encysted individuals of Glinostomum mar- 

 ginatum, Rud. This form has been reported hitherto only from fish and 

 fish-eating birds. The pericardial cavity, especially in frogs during June, 

 was found to contain oval cysts, sometimes grouped in masses, each cyst 

 containing a distome so immature that its generic affinities cannot be de- 

 termined from the data furnished by a study of its structure. It may 

 turn out to be a missing early stage of some trematode whose later stages 

 are already known. The urinary bladder in a considerable fraction of the 

 frogs examined harbors a species much like, if it is not identical with, 

 the Gorgodeda attemiata which Stafford has described from a similar loca- 

 tion in the frogs of Canada. A member of the Ainphistoinidre occurs occa- 

 sionally in the urinary bladder but is more characteristically a parasite 

 of the rectum, where it is found at all seasons. In one instance Gcphalo- 

 gonimus was found in the rectum and small intestines. In a few cases a 



