1880. | Protoplasmic Dynamics. 239 
results while the upper and inner adjacent plasma supplies its 
place to swell and follow, and so on, the mass advances. This 
kind of motion is very common in some Amcebas. ` 
2. Axial Exsertion—The imbibitional swelling may be still 
more local from either external or internal excitation and thereby 
produce pseudopodal protuberation, and in Amcebas we often 
observe the transition from the pseudopodal to the total proces- 
sion. In both cases these animals show a marked circulation 
towards the swelling point in the protruding part. 
3. Lateral Deflection may be produced in any elongated mass 
by lateral superficial imbibitional swelling, as in the ee area 
of the pseudopod x—y causing 
its deflection to r—y’. By this 
method alternating from side to 
side, the vibrations of the pseudo- 
pods of free-swimming, rotating x 
rhizopods and the flagellate and 
ciliate action of infusorians, rotifers 
and other organisms are effected, probably under control of elec- 
tro-chemical impulses in their own substance. The sort illus- 
trated above may be called the monomeric while the polymeric or 
undulatory form also appears 
as shown in the figure, the - 
white swollen regions being 
several and alternately dis- 
posed. Again, should the imbibition follow a spiral line, spiral 
contortions and cycloidal figures result. : 
A good method of showing imbibitional deflection is to use a 
very thin strip of gelatin, such as is employed by lithographers 
for tracings. Let a-b represent the sheet as 
seen edgewise and standing erect, held at a. b 
Now if it be breathed on gently at the point 
indicated by the arrow, it will quickly bend over -7 
to 4’. This is by imbibition of the moisture of R E TN 
the breath on one side causing it to swell. The ; y 
thinner the sheet is the quicker will the flexure - ; 
appear, and by comparison we may judge that 
with filaments as fine as cilia it should result 
with the same rapidity that characterizes cilia aw a 
Motion. The thin mass erects itself as promptly - 
ofits own accord, but still more sudden if moisture be breathed ee 
7 7 
