THE YOtlKO SCIENTIST. 
133 
Marvels of Pond Life— IIL 
WE shall have occasion again to notice 
the Protophytes, and now pass to the 
Protozoa, of which we have a good illus- 
tration in the Vorticella already spoken 
of. In the group before us a number of 
elegant bells or vases stand at the end of 
long stalics, as shown in the accompany- 
ing engraving, while round the ends of 
the bells, the vibrations of a wreath of 
cilia produce little vortices or whirlpools, 
and hence comes the family name. This 
current brings particles of all sorts to the 
accomplished in a well-made microscope 
by turning the mirror quite out of the 
plane of the axis of the instrument, that 
is to say, on one side of the space the 
body would occupy if it were prolonged. 
By this means, and by placing the lamp 
at an angle with the mirror, that must be 
learnt by experiment, all the light that 
reaches the eye has first passed through 
the object, and is refracted by it out of 
the line it was taking, which would have 
carried it entirely awayo Or the object 
may be illuminated by an apparatus 
called a spotted lens, which is a small 
bull's eye placed under the stage, and 
having all the centre of its face covered 
VORTICELLJE. OR BELL FLOWEE ANIMALCULES, 
mouth near the rim of the bells, and the 
creature seems not entirely destitute of 
power to choose or reject the morsels ac- 
cording to its taste. Every now and then 
the stalk of some specimen is suddenly 
twisted into a spiral, and contracted, so 
as to bring the bell almost to the ground. 
Then the stem gracefully elongates again, 
and the cilia repeat their lively game. 
The general effect can be seen very 
well by a power of about sixty linear, 
but one of them from one to two hundred 
is necessary to bring out the details, and 
a practiced observer will use still more 
magnification with good effect. They 
should be examined by a moderately 
oblique light, or most of the cilia are apt 
to be rendered invisible, and also by 
dark ground illumination. This may be 
Vorticella. with pos- 
terior circlet of cilia in 
process of separation, 
300 linear.— Stein. 
Vorticella in process 
of self-division. A new 
frontal wreath in for- 
mation in each of the 
semi-lunar spaces. 
with a plaster of black silk. In this 
method the central or direct rays from 
the mirror are obstructed, but those 
which Gtrike the edge of the bull's eye 
are bent towards the object, which they 
penetrate and illuminate if it is suf- 
ficiently transparent and refractive. An- 
other mode of dark ground illumination 
is by employing an elega.nt instrument 
called a parabolic illuminator, which need 
not be described. 
