the rotifera

flower. What happens to them there we cannot see ; for round the stem is raised a tube
of golden-brown balls, all regularly piled on each other. Some creature dashes by, and
like a flash the flower vanishes within its tube.
We sink still lower, and now see on the bottom slow-gliding lumps of jelly that
thrust a shapeless arm out where they will, and, grasping their prey with these chance
limbs, wrap themselves round their food to get a meal; for they creep without feet,
seize without hands, eat without mouths, and digest without stomachs.
Time and space, however, would fail me to tell of all the marvels of the world
beneath the waters. They would sound like the wild fancies of a child's fairy tale, and
yet they are all literally true; and, moreover, nearly all of them are true of that rotiferous
world which it is my purpose to describe.
But it will be naturally asked by those of my readers to whom the subject is new,
" What is a Rotiferon ? " and no doubt one would say that a book about Rotifera ought to
begin at the beginning, and define precisely what a Rotiferon is.
Precise definition is, however, in such a case, quite out of the question ; for, though it
is easy enough to define the typical form of a natural group of animals, or even to
include in the definition forms that must be placed not far off from the central one, yet
in the ambitious attempt to frame a definition that shall include many families, we find
(as we get farther away from the typical form) that one by one all the positive statements
are disappearing from our definition ; and at last we have nothing left but the mere
shell of a proposition, with everything worth the stating struck out of it.
The Rotifera, then, are small aquatic animals varying from £ to ^^ of an inch in
length, and deriving their name from a wheel-like appearance produced by fine circlets
of hairs seated on the front of their heads. A few species are marine; but the great
majority known to us belong to fresh water, and are to be found in ditches, ponds, reservoirs,
lakes, and slowly running streams, sometimes attached to the leaves and stems of
water plants, sometimes creeping on the algae, sometimes swimming freely through the
water. Although the greater number of the genera resemble each other in the chief
features of their internal organization, so as to form a very natural group of animals, yet
there are several aberrant forms which would render it a difficult matter to include them
all in one precise definition.
This indeed could be done only by introducing so many qualifications and exceptions
to every statement, that the portrait would be rendered too vague for any reader but one
already familiar with the whole subject.
Of the greater number, however, it is enough to say:
(1) That they swim by means of hairs on the front of their heads.
(2) That they possess a simple stomach and intestine ; and peculiar jaws.
(8) That they have muscles which are sometimes striated, and which often pass
freely through the cavity of the body.
(4) That they have a well-developed vascular system.
(5) That their nervous system consists of one ganglion, with nerve threads radiating
to their organs of sense.
(6) That they are dioecious; have ova of two kinds; and do not pass through any
distinct metamorphosis.
Though the above six statements are precise enough, and in the main true, yet it
will be as well for those, who are not versed in the subject, to pass them over for the
present, and first to master the structure of some one typical Rotiferon ; as, when this has
been done, the general conception of a Rotiferon will be easily grasped, and the variations
from the type readily followed and understood.
For this purpose I have selected Brachionus rubens, whose figure is given much
magnified in I'l. A, fig. 1. The genus Brachionus is to be met with almost everywhere.
It is hardly possible in summer to take a dip of water from a garden-pond, or
to gather the algae from its walls, without bringing up some specimen of the genus.
Brachionus rubens is a fairly common species. It is comparatively a large handsome
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