232 
POPULAR SCIENCE REVIEW. 
if it may be so called, appears to relate to the health of the 
creature. The vesicle may be seen stationary for a long time 
when the empty endosarc, with hardly a trace of food in it, is 
pale, and not very distinguishable from the diaphane, but when 
the whole is well nourished the vesicle appears and disappears 
with remarkable regularity. 
The function of this extraordinary arrangement is pro- 
bably in relation to respiration and circulation. Either the 
contents which are drained or sucked out of the surrounding 
endosarc are water, or water and very liquid stuff which will 
eventually become endosarc or diaphane; the contraction re- 
distributes the water, and pumps the results of the simple 
digestion, diffused, as it has been before, again into the mass. 
But it has been observed a few lines back that some change in 
the direction of the streaming of the endosarc, or the protrusion 
of a pseudopodium, frequently occurs immediately after the 
contraction of a vesicle, so that it is quite possible that its 
function refers to the diffusion of a nutritive liquid as well as 
of simple water. All animalcules, and a great many small 
moving things which are classified as water plants, have these 
vesicles, and whilst in some they burst through a tube or 
directly into the surrounding water, those of others, in some 
rare instances, force their contents through radiating canals into 
the body of the creature. It would appear that a definite mass 
of endosarc always maintains itself around the vesicle ; and 
therefore it follows that one particular mass of the protoplasm 
of the creature is endowed with a permanent function, and a 
power of dilating and contracting with rhythm. 
On the other hand, vesicles appear where formerly they were 
not, so that it must be admitted that this interesting power of 
radial expansion and concentric contraction is common to the 
tissue of the Amoeba generally, and that it is a specialized gift 
analogous to the ordinary protrusion of the diaphane, and its 
retraction and curving pointin one direction and then in another. 
A large Amoeba with a very delicate endosarc had been 
feeding on broken-down conferva, spores, and green cells, when 
a tolerably large diatom (fig. 17), a Pinnularia, came in contact 
with its small end. The scanty diaphane then immediately 
increased in quantity and flowed over the intruder, which sank,, 
as it were, gradually into the endosarc, and remained in one part 
of it. After a few minutes had elapsed, a clear space formed 
in the Amoeba around the prey, which immediately began ta 
move in it forwards and backwards after its usual fashion. The 
space was evidently filled with water, and therein moved the 
captured diatom, apparently in no great discomfort. After 
long watching it became apparent that the size of the space, or 
vacuole , as it is termed, increased, and that the diatom became 
