58 WALKER. 



rhodesiense or to that of the development of the schizonts of 

 Schizotrypanum cruzi. According to Salvin-Moore and Breinl, 

 Fantham, and Chagas the round forms of these trypanosomes 

 are developed in the capillaries of the lungs of the infected 

 animals. In Trypanosoma evansi, on the other hand, the round 

 forms are developed chiefly in the spleen and to a lesser extent 

 in the bone marrow. A few of them can sometimes be found in 

 the lungs and other internal organs, where they have probably 

 been carried by the circulating blood. This corresponds to the 

 observations of Buchanan on Trypanosoma himcei. The spleen 

 is always more or less enlarged, congested, and dark in color. 

 Sections of the organ show that the round forms are developed 

 extracellularly in the small capillaries, which are often occluded 

 by them. 



Furthermore, the development of these round forms of Try- 

 panosoma evansi is different from that described in Trypano- 

 soma gambiense and Trypanosoma rhodesiense. Salvin-Moore 

 and Breinl and also Fantham disagree as to the details of the 

 development of these bodies, but both agree that a large part of 

 the trypanosome degenerates and is cast off, and that the round 

 body consists only of the nucleus, blepharoplast, and a small 

 remnant of the protoplasm of the trypanosome. According to 

 my observations the round form of Trypanosoma evansi is made 

 up of the whole trypanosome, with the exception of the flagellum 

 which is cast off. The trypanosome bends upon itself ventrally 

 (Plate I, fig. 2) until the anterior and posterior ends are ap- 

 posed, the halves then fuse to form a round or oval body, around 

 the border of which the flagellum remains for a time attached 

 (fig. 3) . Sometimes by the fusion of the two ends of the coiled- 

 up trypanosome, ring-shaped bodies are developed which later 

 become fused into a solid mass. The flagellum attached about 

 the border of the rounded trypanosome soon becomes detached, 

 leaving the nonflagellated, binucleate body. Therefore, the de- 

 velopment of these bodies in Trypanosoma evansi corresponds 

 more nearly to the development of the forms described by Bu- 

 chanan in Trypanosoma brucei and to the development of the 

 schizonts described by Chagas in Schizotrypanum cruzi. 



These bodies in Trypanosoma evansi (fig. 4) are round or 

 oval, 2 to 5 microns in diameter, stain pale blue, and contain 

 a nucleus and a blepharoplast that stain red with Giemsa's stain. 

 The nucleus may be situated centrally, but more often eccen- 

 trically. The blepharoplast is usually eccentrically placed, often 

 at the side opposite to the nucleus; sometimes it is adjacent to 



