MICROSCOPIC ORGANISMS IN INTESTINAL CANAL. 249 
differences in nutrition, but they also vary in the form and extent 
of the pseudopodial extensions of their substance. In some cases 
isolated thick pseudopodia alone are emitted from the more on 
spherical body (Plate X VIII, fig. 19), while in others this condi- 
tion is exchanged for one in which the body is spread out in all 
directions into an irregular, constantly changing proteplasmic 
flake. Between these two extremes a connecting series of 
intermediate forms exists, and the transition from one to the 
other through these can frequently be observed to take place in 
individual specimens. In the encysted condition, when their 
form is more or less spherical or elliptical, they frequently attain 
a diameter of 25 w or even more, and they may range down- 
ward from this until the diameter only amounts to 8 yu. 
The body-substance is sometimes almost homogeneous, at 
others more or less distinctly granular, due seemingly to the 
presence of extraneous nutritive matter. Changeable vacuoles, 
often of considerable size, may or may not be present ; but a true 
contractile vesicle seems to be almost always, if not invariably, 
wanting so long as they are retained in the original medium. 
Fic. 5.—Large nucleated excretal Amceba x 1000. 
As in the case of the zoospores, considerable variation exists in 
regard to the presence of a defined nucleus. In some cases no 
recognisable traces of such a structure are present, but in others 
a permanent clear nuclear area is visible. ‘This may or may not 
include an evident nucleolus (Fig. 5). When present, the latter 
may attain a diameter of 7 to 9 w. It is circular and appa- 
rently discoid, but in some cases may appear annular from the 
presence of a thickened margin. 
The degree of movement which the Amcebe present in different 
cases varies greatly. In some the movement is extremely 
energetic, the body forcing its way rapidly between the sur- 
rounding masses of debris. In others it is confined to changes 
of form and slow emissions and retraction of protrusions without 
change of place, and in still others the only signs of it present 
are the gradual appearance and disappearance of vacuoles, or 
other indications of content-change. Any direct multiplication 
of Amcebe by division does not appear to occur, or if it do so, 
must occur with extreme infrequency, as, though carefully 
VOL, XXI,—NEW SER, R 
