216 C. CLIFFORD DOBELL. 
aria but alsoin Rana esculenta and Bufo vulgaris.! 
It is quite probable that Trichomastix really also occurs 
in the last two, though I have never as yet encountered it 
there. 
Structure.—Now that I have described the anatomy of 
Trichomastix it will be an easy matter to describe Tricho- 
monas, for the two animals are alike in most respects. The 
only notable difference is that Trichomonas possesses an 
undulating membrane in place of the posterior flagellum of 
Trichomastix. The structure of the animal is shown in 
the accompanying text-figure. It will only be necessary to 
say something in addition about the undulating membrane 
(see also Pl. 2, fig. 16). 
The undulating membrane resembles that of a trypanosome. 
It has a well-differentiated thickened border, which ends 
posteriorly in a free flagellum, as in Trypanosoma. This 
edge stains very intensely with iron hematoxylin, and to a 
less extent with other chromatin stains. In addition to this, 
however, there is also a rod-like chromatic basal structure, 
whose extent and degree of development vary a good deal. 
Sometimes it is represented merely by a few granules, 
arranged in a moniliform manner (as in the lower of the two 
membranes in fig. 20). Both the chromatic edge and the 
chromatic basis take their origin in the blepharoplast. 
The rest of the animal’s organisation is the same as that of 
Trichomastix (cf. figs. 1 and 16, Pl. 2). 
The undulating membrane during life moves like that of a 
trypanosome. It will be superfluous to describe its move- 
ments. 
It is surprising that so much uncertainty should have 
existed regarding the structure of this organella. Grassi (21) 
described it as a flagellum, but later (22) allowed that it might 
be a flagellum united to the body so as to form a kind of 
membrane. ‘The discrepancy probably arose from his having 
observed both ''richomonas and Trichomastix. Stem 
1 And in Hyla arborea (Grassi). 
