443 
This course is unavoidable owing to the confused terminology which 
has grown up in the literature, and also on account of the present 
necessity of making clear the meaning we attach to different names. 
We have further to define our present conception of the nature of 
several structures which the trypanosomes possess. 
When properly fixed, all the animals we have examined present 
an elongated cell form. No anterior or posterior extremity can, except 
in the most arbitrary sense, be defined. I he exterior of the protoplasm 
is differentiated into a thin outer layer or ectosarc (periplast). Among 
the species with which this paper is concerned, the ectosarc is smooth, 
and does not present any definite ridges or stripes corresponding to 
the structure often described in the larger trypanosomes, such as those 
of the frog, and others. 
The protoplasmic structure within the ectosarc consists of a \ery 
coarse spongioplasm (schaumplasma) containing fine staining granules 
embedded in its substance, the meshes of this spongioplasmic network 
being filled by a less stainable cytolymph. It is sometimes said that 
within the ectosarc, and distinct from the deeper portions of the 
spongioplasm, there exists a layer — the endoplasma. We have, 
however, not been able to demonstrate the existence of this sub¬ 
division. 
The permanent cell structures contained within the ectosarc 
consist of a more or less central area, which, when subjected to Breinl s 
stain, assumes a purple colour (see figs. 4, 5, 11, 12, 13)- We propose 
to call the whole of this area the nucleus. Within the nucleus there 
is always to be found a clearly-defined body which stains undei the 
same conditions red, and we propose, for reasons which will become 
more apparent later, to term this body the inlra-nuclear ccntrosome 
(Karyosome, Innenkorper). 
It does not appear to be the case, when the animals arc not 
dividing, that the nucleus can be correctly said to be bounded by any 
definite membrane. In most instances it appears more correct to 
say. that there is no definite membrane, but rather that there is a 
very sharp division between the spongioplasmic network and the 
finer network of the nucleus. 
Near the broad end of the animal’s body there is usually to be 
found a granule, or small group of granules, which stain like the intr 
nuclear centrosome. These, whatever their numbers at any particu a 
