THE YOUNG SCIENTIST. 
7 
as herrings in a tub, and in many portions 
of the field the process of self-fissure, or 
multiplication by division, is going on 
without any symptoms of discomfort on 
the part of the parent creature. This is 
an interesting sight, but we will not linger 
over it, for the sun is shining, and there 
is enough warmth in the air to make it 
probable that the ponds will be more pro- 
lific than in the cold winter months. Sun- 
shine is a great thing for the microscopic 
hunter ; it brings swarms of creatures to 
the surface, and the Rotifers are especially 
fond of its genial beams^ Even if we 
imitate it by a bright lamp, we shall 
attract crowds of live dancing specks to 
the illuminated side of a bottle, and may 
thus easily effect their capture by the 
dipping- tube. 
This year the March sunshine was not 
lost, for on the third of that month I ob- 
tained a bottleful of conferva from a pond 
about a mile from my house, and lying at 
the foot of the Highgate hills. Water- 
fleas were immediately discovered in 
abundance, together with some minute 
worms, and a ferocious-looking larva 
Pterodina patina. 
covered with scales; but what attracted 
most attention was a Rotifer, like a trans- 
parent animated soup-plate, from near the 
middle of which depended a tail, which 
swayed from side to side, as the creature 
swam along. The head exhibited two little 
red eyes ; two tufts of cilia rowed the liv- 
ing disk through the water, and the 
gizzard worked with a rapid snapping 
motion, that left no doubt the cilia'-y 
whirlpools had brought home no slender 
stores of invisible food. Sometimes the 
end of the tail acted as a sucker, and fixed 
the animal tightly to the glass, when the 
wheels were protruded, and the body 
swayed to and fro. Then the sucker action 
ceased, and as the creature swam away, a 
tuft of cilia was thrust out from the ex- 
tremity of the tail. A power of one hun- 
dred linear was sufficient to enable the 
general nature of this beautiful object to 
be observed, but to bring out the details, 
much greater amplification was required, 
and this would be useless if the little 
fidget could not be kept still. 
The size of the creature, whose name 
we may as well mention was Pterodina 
patina, rendered this practicable, but re- 
quired some care. The longest diameter 
of the body, which was not quite round, 
was about 1—120", so that it was visible to 
Pterodina patina— gizzard. 
the naked eye, and as a good many were 
swimming together, one could be captured 
without much difficulty, and transferred 
with a very small drop of water to the 
live-box. Then the cover had to be put 
on so as to squeeze the animal just enough 
to keep it still without doing it any 
damage, or completely stopping its 
motions. This was a troublesome task, 
and often a little overpressure prevented 
its success. 
Some observers always use in these 
cases an instrument called a compres- 
sormm, by which the amount of pressure 
is regulated by a lever or a fine screw; 
but whether the student possess one or 
not, he should learn to accomplish the 
same result by dexterously manipulating 
a well-made live-box. We will suppose 
the Pterodina successfully caged, and a 
power of about one hundred and fifty 
linear brought to bear upon her, for our 
specimen is of the " female persuasion.'* 
This will suffice to demonstrate the dis- 
position and relation of the several parts, 
after which one of from four hundred to 
five hundred linear may be used wn'th 
great advantage, though in this case the 
illumination must be carefully adjusted, 
and its intensity and obliquity "frequently 
changed, until the best effect is obtained. 
We find, on thus viewing the Pterodina, 
that it is a complex highly-organized 
creature, having its body protected by a 
cara,pace, like the shell of a tortoise, but 
as flexible as a sheet of white gelatine 
paper, which it resembles in appearance. 
Round the margin of this carapace are a 
number of little bosses or dots, which vary 
