the rotifera

The Reproductive
System.
The reproductive system of the female is only too conspicuous ; as the presence of a
large ovary (figs. 1, 2, oy), and of one or two opaque ova in different stages of growth,
frequently obscures the sight of the other organs.
The ovary is studded with large and rather irregularly shaped germs (figs. 1,2,0); and
the ova (fig. 1, om), so long as they are within the body, are dark, granular, and homogeneous.
The ovary opens doubtless by an oviduct into the cloaca, but this I have not been
able to see. This is the arrangement that exists in other cases wherever I have seen
the oviduct. The mature ovum is expelled very quickly; and the egg often remains
attached to the animal by a thread till the young escapes by rupturing the shell (if it
may be so termed) in which it is inclosed. If, however, a Brachionus, with two or
three eggs attached, be held in the compressorium, it will frequently free itself by
pushing with its foot against the eggs, and so breaking the threads.
The Egg.
Of the eggs and their development it is unnecessary here to say more than that
B. rubens has two kinds of female eggs, nearly of the same size ; of which the one has a
smooth, transparent, membranous covering or shell, while the other has a thick opaque
shell, ornamented with hemispherical knobs. The former is the ordinary " summer "
egg, and the latter the so-called " lasting," " winter," or " epliippial " 1 egg. In shape,
too, the epliippial egg differs from the ordinary female one. It is much bigger at one end
than the other, and at the smaller end there is a projecting neck and cover (fig. 16).
The male eggs are smooth and semi-transparent like the ordinary female egg ; but
are somewhat rounder in shape, and barely half the size. They occur, too, in larger
clusters; for while it is usual to see only two or three smooth female eggs, or one
epliippial egg, attached to the mother, no fewer than eight or ten male eggs may be seen
carried about together.
The Male.
The young female Brachionus when hatched resembles its mother; but the young
male is a widely different animal (figs. IB, 14). It is about one-third of the length of
the adult female's lorica, and it has neither lorica, mastax, jaws, nor stomach.
The head bears a simple circle of long cilia, and there is a red eye on a cephalic ganglion
placed just as it is in the female. The vascular system, with its tortuous
canals, vibratile tags, and contractile vesicle, is also present; and the foot is furnished
with the usual pair of glands ; but of a nutritive system there is not the slightest
vestige.
Nearly half the body is occupied by a great sperm-sack (figs. 13, 14, ss), in which
under favourable circumstances the spermatozoa themselves may be seen in motion.
The sperm-sack ends in a short protrusile tube, the penis (figs. 13, 14, jo), ciliated at the
end, and placed just above the foot.
In the larger and more transparent males of other genera—notably in that of
Asplanchna Ebbesbornii—there are special muscles for drawing back the protruded
penis ; and, though I have failed to see these in the male of B. rubens, it probably
possesses a similar structure.
This strangely unfurnished creature leads a brief life of restless energy, now darting
from place to place, so swiftly that the eye can scarcely follow it, and now whirling
round as if anchored by its curved foot and penis.
It often circles round the female, attaching itself now here, now there, and forcing its
companion to waltz round and round with it, from the top of the phial to the bottom.
With animals so active and so small it is difficult to be certain of having seen actual
1 So named by Prof. Huxley from the resemblance to the lasting-eggs of the Daphnite. These
latter were called " epliippial " by Miiller from their shape, which is that of an ephippium, or saddle.
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