THE H^EMOFLAGELLATES AND ALLIED FORMS 307 



or trypanomonad type of flagellate. Until the cultural development of a 

 trypanosome has been compared in detail with its natural development in 

 the invertebrate host, it is impossible to estimate precisely the bearing of the 

 cultural series of stages from the point of view of the physiology and mor- 

 phology of the parasite. The only investigator who has attempted this is 

 Chagas (425), who found in cultures of Schizotrypanum cruzi the same three 

 principal phases namely, rounded, crithidial, and trypaniform that occur 

 in the natural cycle, and in the same order of sequence. At present, therefore, 

 it would be unprofitable to discuss in detail the series of forms occurring 

 in artificial cultures, and it must suffice to refer the reader for further infor- 

 mation to the principal works on the subject, namely, those of Novy and 

 McNeal (489), Bouet, Franga (438, 443), Rosenbusch, Thomson (525), Wood- 

 cock (527), Lebedew, and Doflein (431). As already pointed out above, the 

 cultural method is often of the greatest practical value in determining whether, 

 in a given case, an animal is infected with trypanosomes or not. 



Lebedew has described what he believes to be syngamy in the cultural 

 phases of T. rotatorium ; compare also the account of Leishmania below 

 (p. 319). 



The genus Trypanosoma comprises a vast number of species, 

 parasitic in the blood of animals throughout the vertebrate series ; 

 and several attempts have been made to subdivide and classify 



Fia. 133. Endotrypanum schaudinni from the blood of Chdcepus didactylus. 

 A E, Various forms of the intracorpuscular parasite ; F, trypanosome 

 from the blood of the same host. After Mesnil and Brimont, magnified about 

 1,500 diameters. 



this comprehensive genus into smaller groups. Such attempts 

 have either taken the course of splitting off particular forms, char- 

 acterized by some special peculiarity, from the main group, or of 

 subdividing the group as a whole on some principle of morphology 

 or development. An example of the first method is the foundation 

 by Chagas (425) of the genus Schizotrypanum, as already mentioned, 

 for T. cruzi, on the ground that it multiplies by schizogony and 

 possesses intracorpuscular phases. The genus Endotrypanum was 

 proposed by Mesnil and Brimont for a peculiar form which was 

 discovered by them within the red blood-corpuscles of a sloth 

 (Cholcepus didactylus), and which is very probably an intracorpus- 

 cular phase of a trypanosome found free in the blood-plasma of 

 the same host. The life-cycle of Endotrypanum is not yet known. 

 Chagas considers it not improbable that it should be placed in the 



