ON THE YOLYOX GLOBATOE. 
139 
a a a), the pointed end just penetrating the transparent 
sphere (fig. 2, c) ; while the large end points to the centre, 
and is entirely within the cavity (fig. 2). If this drop-shaped 
green body, or, as it is called, “ zoospore, ** be carefully 
examined by a J-inch object-glass, it will be noticed that one 
or two delicate, colourless hairs, or “ cilia ** (fig. 2, b 6), are 
attached to the point which just projects through the 
membrane. It will also be seen that these “ cilia ** move 
about with more or less rapidity. Their lengdh is con- 
siderable — three or four times the length of the zoospore — 
and to the associated movements of all is due the easy rolling 
motion of Volvox. By placing some carmine in the water, 
the direction of the currents produced by the cilia ** can be 
well seen — the granules of the carmine in one part rushing 
towards, in another away from, the Volvox. To what, then, 
is this movement owing ? If we observe the action of cilia 33 
in even animal bodies, we have reason to believe that it is 
owing to chemical changes within, rather than to nervous 
power ; for, after the death of the animal — for instance, the 
common mussel — for three hours, and even to commencing 
putridity, the action of the cilia of the beard or gills has 
been observed. One can hardly doubt but that in Volvox 
they act in concert, when we observe the steadiness with 
which the total movements take place; for at one time it 
slowly moves across the field of the instrument — then it stops 
and simply revolves — then it combines both rotation and pro- 
gression.; but we are ignorant as to what regulates and 
controls this action. 
It may be observed by an oblique light, if not otherwise 
readily seen, that there are lines of communication between all 
the green bodies (fig. 1, a a). The origin of these was at first 
rather puzzling, but observers noticed that in some Volvoces 
the “ zoospores 33 were not always drop-shaped, but some- 
what star-shaped, the rays of each touching the rays of the 
adjoining zoospores (fig. 3). Ultimately these rays were 
retracted, a little line of clear matter only remaining between 
them, while the green body became drop-shaped. This 
peculiar shape of the zoospore is occasionally so marked as to 
lead the early observers to conclude that it characterized a 
distinct species, which was named “ Volvox stellatus;** but 
all the intermediate stages may frequently be seen. 
Let us pay a few moments* attention to this drop-like 
“ zoospore ** (fig. 2 , a a a), using still the higher magnifying 
powers. Formerly they were considered as “ animals/* and 
were classed as Monads ; ** being like them supposed and so 
described, as possessing an eye, mouth, and several stomachs. 
But really no such organs exist. It is true there is frequently 
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