II HABITS AND NATURAL HISTORY OF THE FROG 41 



Species of Strongylus, Nematoxys, and Oxysoma are occa- 

 sionally found in the intestine of frogs, and the ventricle of 

 the heart and the blood vessels may be infested by species 

 of Filaria. The hair worm, Gordius, occurs in the frog 

 among other forms during a part of its larval life. 



The Acanthocephali are represented by one species, 

 Echinorhynchus haruca Rud., parasitic in the intestine of 

 the frog. Another species, E. lesiniformis Malin, has been 

 described in an encysted state in the peritoneum. 



Cestodes are rarely found in frogs. Toznia dispar 

 Goeze, which occurs in the intestine of several European 

 species of Rana, has been found by Leidy * in this country, 

 in the intestine of Rana pipiens and Bufo /entiginosus. 



Frogs harbor several species of Trematodes, which occur 

 chiefly in the intestine and bladder. Loos 2 describes eight 

 species of Distomum from frogs found in Europe, and 

 Stossich 3 mentions ten species of Distomum occurring in 

 Rana esculenta and nine in R. temporaria, but some of 

 these forms have been united by subsequent writers. Several 

 species of Distomum are common to the frogs of both 

 Europe and North America. Distomum variegatum Rud., 

 according to Leidy, occurs in the lungs of Rana pipiens, 

 and D. retusam Dies, in the intestine of the same species. 

 Two forms of D. cygnoides, according to Bensley, are found 

 in the bladder of Rana pipiens, c/amiians, and catesbiana. 

 D. ovocaudatum, according to Nickerson, occurs in some 

 American frogs. Distomum quietum is reported from Rana 

 pipiens by Stafford, and D. heterostomitm from the same 

 species by Wright. A new species, Distomum arcanum, has 



1 Leidy, " Researches in Helminthology and Parasitology," Smithsonian 

 Inst., 1904. 



2 Loos, " Die Distomen unserer Fische und Fr6sche,"i8Q4. 



3 Stossich, " I Distomi degli Anfibi," 1889. 



