1916] i^wezy: The Genera Monocercomonas and Pohjmaxtix 129 



These two forms comprise the oulj' well-authenticated species in 

 this genus, namely, Monocercomonas melolonthae (Grassi) and 31. 

 ceioniae Jollos. 



The life-history of these flagellates is practically unknown. A few 

 stages in the division of M. ceioniae have been figured by Jollos 

 (1911), but these are inadequate to give a fair idea of the actual 

 process. Some cases have been figured in which the axostyle is absent 

 (Franca, 1913). Whether this is due to faulty technique alone or to 

 the probability that it may be absent during some stages in the life- 

 cycle, more extended observation must determine. 



Another flagellate which has been placed in this genus is that de- 

 scribed by Dobell (1909) as Monocercomonas bufonis from the intes- 

 tine of frogs and toads. This organism has a more slender body, is 

 somewhat longer than M. melolonthae, does not possess an axostyle, 

 has a comparatively small nucleus with the chromatin massed in a 

 number of granules or diffused (pi. 16, fig. 6) in a cloud. These facts 

 would make its inclusion with this genus doubtful. Alexeieff (1911) 

 figures the same form from Triton and Axolotl and finds that it pos- 

 sesses a "chromidial" body below the nucleus (pi. 16, fig. 7), a fact 

 still further separating it from Monocercomonas. 



During my own investigations on the flagellate parasites of am- 

 phibian hosts, including frogs and toads, as well as newts and sala- 

 manders, my attention was directed to this flagellate, which is nearly 

 always present and frequently is very abundant. My first observa- 

 tion led me to agree with Alexeief? (1911) in regard to the structure 

 of the organism. A further acquaintance with it, however, soon con- 

 vinced me that a very important and constant part of its structure 

 had been entirely overlooked by both these investigators. This was 

 the very definite cuticle, or pellicle, which is obliquely striated (pi. 

 16, fig. 4). This gives to the body a fairly rigid contour. The presence 

 of a definite cuticle or pellicle is further shown in specimens which 

 are rather overstaiued, by a dark line around the periphery of the 

 body. The striations are regular, parallel, and about the same dis- 

 tance apart in most individuals. 



This fact in its structure still further separates it from Monocerco- 

 monas, and at the same time suggests its relationship with another 

 genus, Polyniastix. 



The Genus Polymastix 



The genus Polymastix was established by Biitschli (1884) for a 

 small flagellate parasitic in the larva of Melolontha vulgaris, oval in 



