117 in that there is a long and comparatively slender form with a free fiagellum, and a short, stout form with hardl)' any free flagellum. (PI. IX, fig. 5, shows a form with the blepharoplast just beginning to divide.) The breadth of the former varies from r2// to 2/u, of the latter from 17// to as much as 5/U, there being a few very stout and swollen-looking forms. These did not seem in any way degenerate, but the appearance they presented was possibly artificial and due to slow fixation permitting of contraction and broadening. The usual breadth of these forms was from 2-5/i to 3/i. A marked feature of this trypanosome was the frequent occurrence of an unstained area, usually of a spherical shape, in the neighbourhood of the blepharoplast. This is, of course, sometimes -4-[- 4 -j-|- I I [ -i #vJ " /yH 4 ' 4 r Si I > ' 4 1/ \ 1 1 , M* Chart II. Curve of measurements of mule trypanosome.

seen in T . gambiense and other species, but I have never known it so frequent or well defined as in this trypanosome. It was specially evident in the short, stout forms, but was occasionally seen in the forms showing a long free flagellum (figs. 4 and 5).

Possibly it is merely the product of a faulty fixation. It will be noticed from the curve that a few dwarf or stumpy forms were present. Whether these indicate that there is a double infection, or whether they are like the so-called ' tadpole ' forms which have been described in T. dimorphon infections, I am unable to say. One of the sick mules accompanied me on my return journey from Loka to Rejaf. At the latter place I had a couple of gerbils on board our floating laboratory. These animals {G. pygargus) are as a rule very susceptible to trypanosome inoculation,* but though " Infection invariably results after inoculation with T. gambiense, T. evansi, T. brucei {pecaudt), and T. pecorum.