THE STRUCTURE OF TRYPANOSOMA LEWISI. 793 
age and contraction of the body-cytoplasm ? These are diffi- 
cult questions to answer, but I think that, so far as the 
trypanosomes in the preparations are concerned, the clear 
zone is shown to be really a space: first, by a comparison of 
the trypanosomes fixed by certain methods, for example, 
Mann’s fluid (figs. 29-35, 77-79, 86, 87), in which a compari- 
son with other preparations shows clearly that the thinness of 
the body is due to an obliteration of the clear area under the 
periplast by shrinkage, so that the periplast comes into 
contact with the axial portion of the cytoplasm; secondly, 
from the frequent creases and folds in the periplast already 
mentioned, indicating the existence of a space under it which 
is either empty or at least not completely filled out. 
Since, on the other hand, no trace of a clearer peripheral 
zone can be seen in the living trypanosome nor in the stan- 
dard preparations, | am inclined to think that the appearance 
of the peripheral clear zone under the periplast is due simply 
to shrinkage of the cytoplasm in preparations, leaving a 
space at the periphery in which the red stain of the 
Romanowsky combination becomes deposited. This con- 
clusion may be supported also on general grounds; it is 
common in protozoa to find a more fluid endoplasm surrounded 
by a less fluid ectoplasm. It is, on the other hand, very 
unusual to find the peripheral region of the cytoplasm of 
more fluid nature than the region situated more internally. 
For all these reasons I am of opinion that the clear space 
seen under the periplast is an artefact, the result of shrinkage 
of the cytoplasm produced by the processes of dehydration 
and clearing, necessary when never-dried preparations are 
mounted in Canada-balsam. No such space is ever found in 
dried-off preparations. 
Apart from the nuclear and locomotor apparatus, the 
cytoplasm contains various enclosures. First in importance 
are certain granules situated chiefly in the inter-nuclear 
region; as itis convenient to employ a distinctive term for 
them, I propose to use the term chromatoid grains.’ 
1 Compare Woodcock, ‘ Quart. Journ. Micros. Sci.,’ vol. 50, p. 229. 
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