7 
flagellum. Thus the thick border of the undulating membrane is con- 
tinuous behind with the centrosome and in front with the flagellum. 
The web of the membrane is difficult to stain and is seen only faintly 
in stained preparations. In a fresh preparation the bod}’, the undu- 
lating membrane, and the flagellum appear to consist of a homogeneous, 
strongly retractile protoplasmic substance possessing marked con- 
tractility. 
A disputed point is the biological relation of centrosome to nucleus. 
Rabinowitsch and Kempner, after a study of numerous stained and 
unstained preparations, especially of the developmental forms of the 
trypanosomes, and after an investigation of the views held in regard 
to the nucleus of the flagellata, came to the conclusion that the cen- 
trosome and nucleus are an interdependent whole which corresponds 
to the nucleus of the other flagellata. They maintain that in the 
early stage of development of the parasite the centrosome and nucleus 
represent a whole which, as the parasite becomes older, breaks into 
two parts which pass to either end of the adult parasite. Thej' con- 
sider the trypanosome’s nucleus as made uj) of two parts more or less 
separated; the small oval spot situated in the hind end of the try- 
panosome they designate the nucleolus, while the larger structure 
found in the front end they call the chromatin heap. 
Wasielewski and Senn (5) think that the centrosome is in no way 
whatever connected with the nucleus. They consider the trypanosome 
as made up of two parts, the “jDlasma” and the “periplast.” The 
plasma is the body of the parasite containing the nucleus. The x^eri- 
plast is the outer covering of the trypanosome and embraces the cen- 
trosome, undulating membrane, flagellum, and an outer coat invest- 
ing the body of the parasite. According to this view the centrosome 
is intimately connected with the undulating membrane. It is the 
root from which the thickened free border of the undulating mem- 
brane springs and has nothing to do with a nucleolus, as Rabinowitsch 
and Kempner point out, nor with a micro-nucleus, as held by Plimmer 
and Bradford. In their illustrations the outer coat of the iDarasite 
takes a different stain from the body plasma. 
Laveran and Mesnil mention that blood kept some time shows try- 
panosomes reduced to centrosome and flagellum, and that the con- 
tinuity of the centrosome and flagellum can be seen. We have seen 
the same thing in stained preparations of fresh blood. 
CYCLE OF DEVELOPMENT. 
We kept fresh blood in hanging drop at room temperature and at 
37° C. and watched it for hours without seeing any of the parasites 
advance in development beyond the stage which they ]3resented when 
the blood was first drawn. The different stages of development can 
be seen only with the help of animal experiments. It is very doubt- 
ful if multiplication of the organisms occurs outside the body. 
