MOVEMENTS OF SIMPLE ORGANISMS. Su 
face of the cell-wall and shrinks together so as in a short time to present the 
appearance of a sphere occupying the middle of the cell-cavity. Again, just as 
this contraction is an instance of a special form of protoplasmic motion, so also 
the further change which the contracted protoplast in a cell of Spirogyra under- 
goes is redueible to displacements in its substance, and must be mentioned as 
a special kind of protoplasmie movement. For the conglomerated protoplast 
remains but a short time in the middle of the cell-cavity. It leans almost 
immediately to one side, thrusting itself into a protuberance of the cell-mem- 
brane, which is concurrently developed, and which, when further developed, forms 
a passage leading over into another cell-cavity. Its body becomes longer and 
narrower, and at last slips through the passage into the next cavity, where a 
second protoplast awaits it; and the two then unite, fusing together into one 
mass. It is not premature to remark that all these displacements and invest- 
ments of the protoplasmie substance in cells of Spirogyra, including the pheno- 
mena of contraction, as well as those of pushing forward, escape, and coalescence, 
are not produced as the results of a shock, impulse, or stimulus from without, 
but are to be looked upon as movements proper to the protoplasm, and resulting 
from causes inherent in the protoplasm. 
MOVEMENTS OF VOLVOCINEA, DIATOMACE, OSCILLARLA: 
AND BACTERIA. 
Very remarkable is the movement of those wonderful organisms which are 
comprised under the name of Volvocinew. One species, Volvox globator, was 
known to so ancient an observer as Leeuwenhoek; but he, and after him Linnzeus, 
took it to be an animal on account of its extraordinary power of locomotion, and it 
was named the “globe-animalcule.” A Volvox-sphere consists of a large number of 
green protoplasts living together as a family and arranged with great regularity 
within their common envelope. They appear to be disposed radially, and to be 
linked together and held firm by a net-work of tough threads, their poles being 
directed towards the centre and the periphery of the sphere respectively. From 
the peripheral extremity, which in each protoplast is marked out by a bright red 
spot, proceed a pair of cilia, and these protrude through the soft gelatinous 
envelope of the whole sphere, and move rhythmically in the surrounding water. 
A Volvox-globe rolls along in the water propelled by regular strokes, like a boat 
manned by a number of oarsmen, as soon as the protoplasts, which form the crew 
of this strange vessel, begin to manipulate their propellers. The effect is exceed- 
ingly graceful, and has justly filled observers of all periods with astonishment; 
indeed no one seeing for the first time a Volvox-sphere rolling along can fail to be 
impressed and delighted. 
Another plant allied to the foregoing, the so-called “red-snow,” has always 
excited wonder in no less degree from the remarkable phenomena of motion which 
it exhibits, but also because of its characteristic occurrence in situations where one 
