920 
allowed to come in contact with motile amcebe are quickly taken up in 
quantities sufficient to stain various internal portions of the ameeba a 
decided pink color, without at all staining the ectosarc. In resting 
amcebe this process is much slower and less complete, and here, in ad- 
dition, the ectosare is usually stained. However, in encysted types this 
stain does not penetrate to the interior of the parasite, but may slightly 
color the cyst wall. When, at times, one is fortunate enough to see a 
ruptured cyst in the culture, the neutral red, entering through the open- 
ing, colors the contents and often the inner portion of the ruptured ecto- 
sarc. This observation tends to show that the variations in staining are 
due to permeability of the ectosare rather than to changes in the inter- 
nal structure of the amceba and further indicates that the outer portion 
of the ectosare itself is more dense and resistant than the inner. 
A further most interesting phenomenon with neutral red solutions may 
sometimes be noted in motile amcebe, in which the first granules to show 
color may be those in a persistent pseudopod. If this is due to the thinned 
portion of the ectosare being more permeable, which appears to be the case, 
it might also further indicate that, in addition to the function of locomo- 
tion which the pseudopodia possess, we must consider them as playing a 
part in the metabolism of the parasite—such as the absorption of food. 
Some, at least, of the numerous phenomena of the ectosare may be 
explained by physical laws and their application to the age, environment, 
etc., of the parasite. However, in addition to this we probably have 
changes due to vital metabolic phenomena and perhaps others due to 
variety in species. 
(c) Endoplasm.—The endoplasm is probably composed of a network 
and of fluids in which are embodied the nucleus, vacuoles, spores, granules, 
and other vital parts of the parasite, often together with red blood cor- 
puscles, bacteria, and other foreign bodies. The proportionate amount 
of endoplasm as compared with the whole parasite varies with its envi-- 
ronment and the stage of its life cycle in which the observation is made. 
Apparently its quantity is smallest and its density greatest in the 
encysted stage of the amceba. In the small, young parasite it appears 
homogeneous, and stains easily and intensely, but at later stages it often 
begins to show granulation, vacuoles, foreign bodies, etc., until in the 
eneysted condition of the amceba it often appears to be contracted and 
more sharply distinct than at the beginning. It may or may not be dis- 
tinguishable from the ectoplasm; sometimes the distinction is well 
marked and the outer margin may appear almost as if surrounded by 
a limiting membrane. ‘There may be no apparent color in the endo- 
plasm, or, again, various shades of dull-grayish or greenish refraction may 
be noticed. This variation in color and refraction has already been dis- 
cussed. Ameebe from cultures may be made to take on the so-called 
“ diagnostic,” greenish refraction with almost as much certainty as they 
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