15 
masses of the water Amoebae, but remain stiff. The outer surface is wrinkled 
into folds, meeting and crossing each other when the animal collects its 
endosarc into a globular mass of comparatively small size, (as, for instance, 
when resisting the pressure of the covering glass, ) exhibiting great contractile 
power. After a moment of rest, the animal projects its sarcode in a broad 
stream towards some point of its periphery, while at the opposite point the 
sarcode contracts and governs the direction of the forward movement until 
the animal falls over by change of its centre of gravity, and thus, by a series 
of rolling movements, it makes its way.* The projected arms appear to seek 
the free spaces between the particles of earth or sand in which the creature 
is moving, and thus the direction of movement follows the line of least 
resistance. The movement results from the strong contraction of the ectosarc 
at the point opposite to that of the yielding surface, which allows the 
endosarc to be pressed forwards. During these movements the whole of the 
interior can be seen in turn, and peculiarities of structure are thus best 
observed. 
The distinction between the tough ectosarc aud semi-fluid inner mass is 
much more marked in land than in water species of Amoebae. Greef remarks 
that the body must be composed of two kinds of plasm greatly varying in 
cousistence and physical appearance ; the outward hyaline ectosarc, firm in 
substance, the inner mass soft and granular. 
Wallich and Carter have noticed a similar differentiation even in water 
species. Wallich distinguishes the outer and inner portions as ecto and 
endosarc, but appears not to have found any differentiation of contractile 
capacity or physical constitution. Carter recognises a difference of substance 
and property between the outer and inner sarcode. In the clear ectosarc, 
which, according to Carter, has a distinct membranous envelope, he places 
the locomotive and prehensile power, whilst in the soft endosarc he recognises 
a loose movement of the organic particles on each other — i. e. a rolliag 
movement. Carter also considers that the ectosarc is chemically as well as 
physiologically different from the endosarc, having found that the ectosarc 
turns purple on application of iodine. 
In freah water Amoebae, the inner sarcode is often, during forward movement, 
projected through the outer rind to its very edge. This is not the case with 
the land Amoebae. The layer of ectosarc forming the boundary of the 
* This movement cannot be called creeping. When, by a change of centre 
of gravity, the animal rolls over, the firm protuberances do not yield or 
flatten, but present blunted ends, on which, as on points of leverage, the 
creature is upheld in its rolling gait backwards or forwards, The movement 
is often very active, and carried on with energy and grace. 
