Parasitism in the Frog 207 



teased out with the greatest difficulty, and when isolated, were glisten- 

 ing white in color, ranged in length from one to three inches, and pos- 

 sessed a well defined scolex with four suckers but no hooks. These 

 Cestodes were also peculiar in having a cylindrical body. The available 

 records of Anuran Cestodes list but three species from this country. 

 These are, Nematotaenia dispar Goeze 1782, Taenia pulchella Leidy 

 1851, and Cylindro taenia americana Jewell 1916. Jewell" considers the 

 last two identical, and also questions the occurrence of Nematotaenia 

 dispar in North America. If these contentions are valid then the Ces- 

 todes under discussion are either a new species or identical with Cylin- 

 drotaenia americana. They unquestionably belong to the Nematotae- 

 niidae, even though from their immature condition the species could not 

 be determined with certainty. 



The second (fig. lb) shows the larva of Clinostomiim niarghiatiim^ 

 taken from a subcutaneous cyst. These forms always occur encysted 

 singly, and are very abundant, it being nothing unusual to find several 

 dozen in a single frog. From personal observation it would appear that 

 two species are concerned. The first is a relatively large form with a 

 smooth cuticle, while the other is a smaller, more slender form, with 

 a spiny cuticle. It may be that these are different stages in the develop- 

 ment of the same species. A fair degree of dexterity is needed to sep- 

 arate these forms from their tough membranous sheaths without in- 

 jury. However, when once liberated they are active and extensile to a 

 degree. In conducting the experiments already outlined, three of these 

 Clinostomes and one Cestode were found that showed infestation, pre- 

 sumably with the same species of parasite. The illustrations for the 

 figure were prepared from specimens mounted in toto, and stained with 

 equal parts of acid carmine and alum cochineal. Attempts to measure 

 living material were unsuccessful as these animals changed their shape 

 too rapidly to yield accurate results. 



The parasite found infesting the above forms was a diminutive 

 larval Distome shown in figue Ic. In this case the specimen was teased 

 out of one of the Clinostomes already mentioned and this illustration, 

 like the others, was drawn to scale from a prepared mount. Careful 

 search elicited the presence of these parasites in practically every frog 

 examined, while in some individuals literally hundreds were found. 

 These forms were active, free-living, and migrated extensively through- 

 out the tissues of the host. The easiest way to obtain them in number 

 was to scrape the inverted skin of a frog in normal salt solution. In 

 the fine residue thus obtained numerous Distome and other larval Tre- 

 matodes could usually be found under the microscope. Living speci- 

 mens showed a well defined forked digestive tract and an emulsified 

 structure of the protoplasm. They were unusually active and extensile, 

 changing their shape continually in the process of locomotion. They 

 were also more slender than the drawing would indicate, as the mounted 



2 Jewell, Minna E. Cylindrotaenia americana nov. spec. Fiom tiio Cricket Fros. 

 Jour. Parasit., 2:181-191. 1916. 



- Osborn, H. L. On the Distribution And Mode Of Occurrence in The United States 

 And Canada Of Clinostomum Marginatum, A Trematode Parasite In Fish, Frogs And 

 Birds. Biol. Bull. No. 5, Vol. XX, pp. 350-367. 1910. 



