176 
Triarthra longiseta. 
[Monthly Microscopical 
[.Journal, March 1, 1869. 
V. — On Triarthra longiseta. By C. T. Hudson, LL.D. 
Plate VI. 
Teiabthea longiseta swarmed this snmmer in a farm-yard pond, 
near Portbury, and gave me an excellent opportunity of trying to 
add to the rather meagre stock of information that at present exists 
concerning this curious rotifer, as well as of attempting to do some 
justice to its singular figure. 
The trochal disc is of an oval shape, and bears in its centre one 
large conical prominence, with a lesser one on either side of it ; and 
on each of these latter is peated a red eye. An unbroken row of 
cilia fringes the disc ; and by means of these, Triarthra swims slowly 
forwards, in the direction of its length, and at the same time turns 
gently round its longer axis. When it reaches the edge of the water 
in which it is confined, or for any other reason wishes suddenly to 
change its course, it jerks forward three spines, two of which spring 
from beneath the trochal disc, and the third from the lower portion 
of its ventral surface. The third spine is, indeed, where the pseudo- 
podium is usually placed, and owing to the absence of which Triarthra 
is forced to be perpetually in motion. 
Just under the edge of the trochal disc, and on the ventral sur- 
face, is the aperture of the buccal funnel (Fig. 1, a). It is formed 
by a fold of the cuticle, and is shaped like a watch-pocket, having its 
edge and inner surface lined with cilia. The funnel slopes backwards 
and upwards towards the dorsal surface, to meet the mastax. This 
latter is furnished with jaws similar to those of Melicerta, and con- 
taining about twenty pairs of slender parallel rods attached to the 
incus (Fig. 2). From the mastax proceeds a long narrow tube to 
the stomach, which has very thick walls, and the lower third of 
which is divided from the upper portion by a deep constriction. 
This lower portion is densely covered with long cilia, and the food 
which enters it is soon afterwards expelled into the cloaca. On the 
upper portion of the stomach are seated two saddle-shaped gastric 
glands (Fig. 1, h ; and Fig. 3), clear aiM almost colourless, and with 
what appear to be oil globules embedded in the surface. 
The ovary is generally large, and stretches right across the body, 
usually containing one large egg and a multitude of undeveloped 
germs. It opens into the cloaca ; and each egg, when sufficiently 
matured, is expelled, with a sudden violent effort, so quickly that 
the eye can scarcely follow the process. The eggs remain attached 
for some time, by slender threads, to the parent ; and Triarthra is 
generally to be found vdth two or three eggs adhering to it. 
The muscular system of Triarthra is very remarkable (Fig. 4). 
One powerful band (Fig. 4, a) passes round the neck, and from 
