N. H. Swellengrebel and C. Strickland 
387 
see if the gut contained any natural flagellates, but nothing was to be 
seen. Professor Nuttall informs us that he has dissected at least 
80 bugs for other purposes but never found any trace of natural 
flagellates. So we may be sure that the forms found in our bugs 
really belonged to T. lewisi. 
Two bugs were fed on a lewisi-rat in the chronic stage of infection. 
On the third day after the infective meal, bug No. 1 was dissected. 
The posterior end (black blood) and the anterior end (red blood) of the 
midgut were swarming with flagellates. 
Stained preparations showed: 
(а) Forms with a broad hind end, the blepharoplast situated close 
to the nucleus (Diagram XXI, Figs. 1—2). 
(б) Forms with a hind end much broader than in type a (Figs. 3— 
5), the blepharoplast situated behind, beside or before the nucleus. 
The front end of the flagellate is generally very slender. Fig. 4 
represents a rather extreme form, which was to be seen also in the 
living preparations. 
(c) Ordinary crithidiae (Figs. 6—8). 
Figs. 1—5. Formation of club-shaped forms. 
Figs. 6—8. Crithidiae. 
Bug No. 2 was dissected nine days after feeding (kept in a gauze 
bag at 13—16° C.) and contained flagellates only in the anterior part of 
the midgut. They were of the true crithidiae type, possessing a slender 
rod-like body, no apparent undulating membrane and a long free fla¬ 
gellum. They were not so frequent as in bug No. 1. The stained 
preparation was unhappily destroyed, the blood film being washed off, 
but judging from the living specimens the aspect was the same as that 
of the flagellates represented in Figs. 6—8. No club-shaped forms 
