120 Uiviversifii of California P)i,blicafioiis in Zoologij [Vol. 16 



rolled-up form of the trypanosome phase of T. lewisi prior to its 

 entrance into the epithelial cell for multiple fission. "We have no 

 evidence, however, that the erithidial phase of T. triatomae enters the 

 cells and undergoes multiple fission in that phase, but the possibility 

 of this is certainly suggested by the sequence of elavate to rolled-up 

 individuals found in the stomach of Triatoma protracta. This series 

 as represented in our material seems to involve a progressive enlarge- 

 ment of the posterior region at the expense of the anterior (pi. 14, 

 figs. 14-19), the bending of the posterior end around anteriorly (pi. 

 15, fig. 20) and the fusion of the two limbs of the U-shaped body into 

 one oval structure (pi. 15, fig. 21), in which the only trace of its 

 method of origin is the bent chromatic axis of the flagellum. This 

 oval stage was found by us in smears. No trace of its intracellular 

 occui'rence could be detected in our smear preparations. There is 

 the possibility that the process may be one of unrolling rather than 

 of rolling up, but the parallel in T. lewisi suggests the probability of 

 the former, with the corollary of intracellular invasion and jiossibly 

 even of multiple fission in this ci'ithidial phase. 



4. The stotit type. — This is similar in proportions to the hapto- 

 nionad forms in T. lewisi, which attach themselves by their flagella 

 to the rectal surface and undergo there repeated binary fissions. One 

 instance of spindle formation in a short, stout form (similar to that 

 in pi. 15, fig. 28) has been found in our preparations. The degree 

 of haptomonad attachment among the rectal forms as observed in 

 living material through the wall was much less in our restricted 

 material of T. triatom.ae than it was in Crithidia leptocoridis Mc- 

 Culloch (1915), or than in T. lewisi as described by Minehin and 

 Thomson (1915). 



It seems probable, however, that the series of forms of decreasing 

 size and increasing stoutness shown in our figures 23-30, plate 15. 

 represents a transition to the haptomonad phase, or at least to one 

 corresponding to that stage in T. lewisi. However, all of the members 

 of this series, from the very large individual with central median 

 nucleus (pi. 15, fig. 23) to the short stumpy form (fig. 28), are found 

 in the stomach and only the smaller ones in the rectum. The nucleus 

 does not progress so far posteriorly here as in the rolled-up type and 

 the parabasal becomes somewhat more condensed as compared with 

 the earlier erithidial types, and thus more like that of the rectal 

 ti-ypanosome forms (cf. figs. 30 and 41). 



