302 KOFOID AND SWEZY. 



larger chromatic basal rod and in appearance the projecting flagellum 

 is a continuation of both. That the posterior flagellum is, however, 

 the projecting part of the chromatic margin only, is proved by the 

 fact that when the latter is torn loose it carries the projecting flagellum 

 with it as its distal part. 



The undulating membrane {und. m., Fig B) is a thin hyaline proto- 

 plasmic film, less granular than the general mass of cytoplasm, and 

 apparently composed only of its outermost layer or pellicle. It, 

 however, differs from the pellicular region elsewhere in that it does 

 not take on amoeboid activity ; always retaining, except as the animal 

 is disintegrating, its dift'erentiated and characteristic structure and 

 undulating movements even tliroughout the protean conditions of the 

 pre- and postmitotic phases and during the period of its own longi- 

 tudinal division. In its outer margin lies the posterior flagellum 

 differentiated as a chromatic margin and at its base the chromatic 

 basal rod. In evolution, origin, and function this membrane is the 

 result of the inclusion of an outgrowing postei'iorly directed flagellum, 

 whose activities raise the surface layer or pellicle above the level of 

 the cytoplasm and result in its differentiation. 



The blepharoplast also gives rise to another deeply staining out- 

 growth, the chromatic basal rod (chr. bas. r., Fig. B) or parabasal 

 body, lying at the base of the undulating membrane. Although this 

 follows the spiral course of the membrane (PI. 1, Figs. 3, 5) it is never 

 thrown into undulations and appears to have no motor activity, 

 though subject to modifications in curvature and in location during 

 the postmitotic period, shifting position with the whole extranuclear 

 motor complex. With the undulating membrane it lies opposite to 

 the cytostome, that is, in the dorsal side of the body and gives to that 

 side, especially in rounded-up phases and in fixed material, a greater 

 convexity than the ventral. In this curvature the axostyle generally 

 shares. This chromatic basal rod is of uniform caliber throughout 

 and takes nuclear stains generally. It does not, even under extreme 

 decolorization, break up into chromatic blocks though in its origin 

 by outgrowth its distal end may at first form by the fusion of fine 

 chromatic granules. 



The chromatic basal rod or parabasal body is found apparently 

 throughout the genus Trichomonas. It is figured in T. lacertae by 

 Prowazek (1904), in T. muris by Wenyon (1907), in T. bafrachorum 

 by Dobell (1909) as a thread and row of adherent chromatin granules, 

 in T. eberthi by Martin and Robertson (1911), in T. augusta by Alex- 

 eieff (1913), in T. caviae, T. muris, and T. augusta by Kuczynski 



