451 
indifferent forms described by Schaudinn * Minchin.t and many other 
authors. The present examination of the forms appearing in the 
blood leads us to believe that there is to be found among these 
trypanosomes a series extending from those which are relatively 
small, to those which are relatively immense. T he three forms often 
described and alluded to as distinct, consequently appear to be 
arbitrarily chosen examples in a continuous series of dimensions. 
Multiplication tn the Blood 
From the time when the parasites appear in the blood of an 
infected animal until their numbers reach any particular maximum, 
rapid multiplication takes place by longitudinal fission of the 
individual trypanosomes, the multiplication being most rapid near the 
successive periods of maximum numbers. When the parasites are not 
dividing, they present the appearance represented in figs, i and 4. 
The nucleus is nearly in the middle of the long axis of the cell, 
and consists of an outer stainable mass, enclosing generally a lighter 
central area, within which there lies a small, sharply-definable body, 
which stains red in contrast to the purple colour of the outer mass 
when subject to Breinl’s stain. This central structure forms the 
intra-nuclear centrosome (karyosome). At the broad end of the cell 
there exists another staining granule which, when the cell is not 
dividing, remains single, the granule in question forming the extra 
nuclear centrosome (blepharoplast, micro-nucleus, centrosome). It 
stains, under the above conditions, like the intra-nuclear centrosome. 
Arising directly from the extra-nuclear centrosome, there extends a 
delicate thread, which stains more faintly, but in the same manner as 
the centrosomes. It is enclosed in a thin expansion of the 
ectosarc running along the entire length of the cell. The thread 
projects at the narrow end of the cell as a long stained whip-lash. 
This thread forms the so-called flagellum, and the ectosarca 
expansion the undulating membrane. 
The first sign of an approaching fission is generally apparent m 
relation to the extra-nuclear centrosome. From this there buds ou 
small fragment, figs. 1, 2, and 3, which may become flattened, as m 
* Loc. cit. 
t I’ro. Roy. Soc., 1907. 
