126 
THE YOUNG SCIENTIST. 
evidence of their not liaving been dis- 
covered, and tlie complete absence of 
" vessels " cannot be affirmed. 
In the last edition of " Pritchard's In- 
fusoria," to which some of our ablest na- 
turalists have contributed, after separa- 
ting two groups, the Desmids and the 
Diatoms, as belonging to the vegetable 
world, the remainder of the original 
family of infusoria are classified as Fhyto- 
zoa, Frotozoa, Botlfera, and Tardigj-ada. 
We shall explain these hard names im- 
mediately, first remarking that the Des- 
mids and the Diatoms, concerning whom 
we do not intend to speak in these pages, 
are the names of two groups, one dis- 
tinctly vegetable, while the other, al- 
though now generally considered so, w^ere 
formerly held by many authorities to be 
in reality animal. The Desmids occur 
very commonly in fresh water. We have 
some among our Confervas. They are 
most brilliant green, and often take forms 
of a more angular and crystalline charac- 
ter than are exhibited by higher plants. 
The Diatoms are still more common, and 
we see before us in our water-drop some 
of their simplest representatives in the 
form of minute boats made of silica (flint) 
and moved by means still in dispute. 
Leaving out the Desmids and Diatoms, 
we have said that in Pritchard's arrange- 
ment the views of those writers are 
adopted who divide the rest of the in- 
fusoria into four groups, distinguished 
with foreign long-tailed names, which we 
will translate and expound. Eirst come 
the Phytozoa, under wdiich w^e recognize 
our old acquaintance Zoophyte turned 
upside down. Zoophytes mean animal- 
plants, Phytozoa mean plant-animals. We 
shall have by-and-bye to s]ieak of some of 
the members of this artificial and unsatis- 
factory group, and postpone to that time 
n learned disquisition on the difference 
between animals and plants, a difference 
observable enough if we compare a hip- 
popotamus with a cabbage, but which 
"grows small by degrees, and beautifully 
less," as w^e contemplate lower forms. 
After the Phytozoa come the Protozoa, 
or first forms in which animality is dis- 
tinctly recognized. Under this term are 
assembled creatures of very various or- 
ganization, from the extreme simplicity 
of the Proteus or Amoeba, a little lump of 
jelly, that moves by thrusting out portions 
of its body, so as to make a sort of extem- 
pore legs, and in which no organs can be 
discerned,* up to others that are highl\- 
developed, like our Vorticellce. This 
group is evidently provisional, and jum- 
bles together objects that may be widely 
separated when their true structure and 
real affinities are discerned. 
EoUowing the Protozoa come the Pio- 
tifera, or Wheel-bearers, of which we have 
obtained an example from our pond, and 
whose characteristics we shall endeavor 
to delineate when our specimen is under 
view ; and last in the list we have the 
Tard'ujrada, "Slow-steppers," or Water 
Bears, queer little creatures, something 
like new-born puppies, with a double al- 
lowance of imperfect feet. These, though 
somewhat conected with the rotifers, are 
considered to belong to a low division of 
the arachnida (spiders, etc.) 
Peeling that wx^ must be merciful with 
the long-tailed words and explanations of 
classification, w^e reserve further matter 
of this kind for the opportunities that 
must arise, and direct our attention to 
living forms by watching the Englenw 
which our water-drop contains. We have 
before us a number of elegant spindle- 
shaped bodies, somewdiat thicker in front 
than behind, and in what may be called 
the head there glitters a brilliant red 
speck, commonly called an eye-spjot, al- 
though, like the eyes of potatoes, it can- 
not see. Bound this e^^e-spot the tissues 
are clear, like glass ; but the body of the 
creature is of a rich vegetable green, whicli 
shines and glistens as it catches the light. 
Some swim rapidly wdth a rollicking- 
motion, while others twist themselves 
into all manner of shapes. Now the once 
delicate spindle is oddly contorted, now it 
swells out in the middle, like a top, and 
now it rolls itself into a ball. The draw- 
ings will afford some idea of these protean 
changes, but they must be seen before their 
harlequin character can be thoroughly ap- 
preciated. Some of the specimens ex- 
hibit delicate lines running lengthwise, 
*In some kinds and in some stages of growtli 
this is not strictly true. 
