50 WALKER. 



parasite may be pressed more or less into the surface of the 

 plastic corpuscle and appear as if intracorpuscular in the stained 

 preparation. The merozoites of Trypanosoma evansi, so far as 

 my observations show, develop extracorpuscularly and directly 

 into adult trypanosomes. 



No sexual process has been observed preceeding or during 

 the formation of the round bodies from the trypanosomes, nor 

 during the development of the multinuclear cysts. Moreover, 

 the sexual reproduction of trypanosomes should, according to 

 the accepted theory, take place in the invertebrate host. The 

 merozoites of Trypanosoma evansi do not show the dimorphism 

 described by Chagas in Schizotrypanum cruzi, nor have I ob- 

 served any evidence of a sexual differentiation in the adult 

 trypanosomes. Therefore, I shall provisionally designate this 

 reproductive process in Trypanosoma evansi as a schizogony. 

 The occurrence of the young schizont (round or "latent") stage 

 in Trypanosoma gambiense, Trypanosoma rhodesiense, Try- 

 panosoma brucei (pecaudi) , and Trypanosoma leptodactyli indi- 

 cates that this schizogony is a general reproductive process in 

 the Trypanosomata. 



The genus Schizotrypanum established by Chagas for the para- 

 site of South American trypanosomiasis of man may have to 

 be abandoned. Its chief differential character from the genus 

 Trypanosoma appears no longer to exist. The so-called intra- 

 corpuscular stages of Schizotrypanum cruzi have been observed, 

 also, in Trypanosoma brucei and in Trypanosoma evansi. In the 

 last species the parasites, although apparently within the cor- 

 puscle, are really extracorpuscular. The schizogony of Schizo- 

 trypanum cruzi described by Hartmann in the endothelial cells 

 of the lung has been observed in Trypanosoma leptodactyli by 

 Carine in endothelial cells in the blood from the heart of an 

 infected animal. This so-called schizogony consists in both cases 

 of hypertrophied endothelial cells containing a large number of 

 the round or "latent" forms of the trypan osome. It appears 

 to be a case of phagocytosis of the young schizonts by an endo- 

 thelial macrophage. Phagocytosis of the trypanosomes, of the 

 round forms, and occasionally of the large schizonts by the 

 macrophages appears to be a common phenomenon in trypano- 

 somiasis; indeed, this is the fate of most of the trypanosomes 

 when they disappear from the blood in the latent phase of the 

 disease. The absence of multiplication by simple division in the 

 peripheral blood would appear to be distinctive of Schizotry- 

 panum cruzi; but, in view of the fact that this parasite appears to 



