6 THE ROTIFERA. 
T. Lonetseta, Hhrenberg. 
(Pl. XIII. fig. 6.) 
Triarthra longiseia 4 5 Ehrenberg, Die Infus. 1838, p. 447, Taf. lv. fig. 7. 
7) 5 7 ‘ Hudson, Mon. Micr. J. vol. i. 1869, p. 176, pl. vi. 
- _ 3; 0 5 Grenacher, Siebd. wu. Kill. Zeits. Bd. xix. 1869, p. 491, Taf. 
XXXvVii. fig. 3. 
SP. CH. Body oval; buccal orifice prominent but not beaked, cup-shaped ; spines 
more than twice the length of the body; eyes wide apart; esophagus long. 
The habit of this interesting creature is to swim slowly forward while turning round 
its longer axis, and every now and then to dart out of its course by jerking forwards the 
three long spines which usually trail behind it. The corona is oval, and bears in its 
centre one broad, low prominence, with a smaller one on either side of it; and just within 
each of these latter is placed a red eye. The buccal orifice is cup-shaped and has its 
inner surface lined with cilia. The buecal funnel slopes backwards and upwards towards 
the dorsal surface to meet the mastax, whose trophi are almost identical with those of 
Melicerta ringens. The esophagus is long and narrow, and the stomach and intestine 
are usually separated by a deep constriction. The gastric glands (fig. 6a) are curiously 
shaped, and frequently studded with what appear to be oil-globules. The vascular 
system is delicately transparent, and difficult to be seen. Ihave traced the lateral canals 
on each side, for some distance down the trunk, from a plexus of tubes in the neck, and 
have detected just there a vibratile tag. I failed to discover the contractile vesicle, but 
Dr. Grenacher (Joc. cit.) has seen it, in its usual position, close to the cloaca. There isa 
large ovary ; and the newly laid eggs remain attached to the parent by a thread for some 
time after their exclusion. The ephippial eggs (fig. 6f) are as curious in shape as the 
gastric glands, and are protected by a thick layer of yellowish transparent cells. By 
bringing into focus the central inner portion of the head, seen sidewise, a bluish and 
roughly rhomboidal mass may be observed; this is the nervous ganglion, and above it 
are the eyes, and from it threads extend to a setigerous fossa in the neck, as well as to 
rocket-headed antenne, one on each side (fig. 6e) just under the surface. Hach eye 
(fig. 65) is a clear, colourless, refracting sphere 5, inch in diameter, resting on, and 
partly imbedded in, a flat plate of red pigment. The longitudinal muscles-are very 
powerful, and are strongly striated; the strie not being straight transverse lines, but 
irregular obliquely transverse curves (fig. 6c). Indeed they appeared to me to alter both 
in direction and in size as I looked at them, giving me the impression that I was looking 
at illusory strie, produced possibly by looking through separated sheets of striated fibre, 
lying over each other. There is an unusually powerful muscular collar running round 
the neck. The spines are stiff quill-like appendages, broadest at their attached bases, 
and tapering at their free ends. The bases (fig. 6d) are like quills that have been 
obliquely cut across, and it is by these cut surfaces that they are attached, one on each 
side of the corona, just above the neck; and one on the ventral surface, at the spot from 
which the foot springs, in those Rotifera that possess one. The spines are notched here 
and there (fig. 6d), and finely imbricated towards their tips. On looking at fig. 6, it will 
be evident that if the muscular collar round the neck be suddenly contracted, and the 
head withdrawn, the spines will be first dragged across the stiff edge of the trunk, 
below the collar, and then jerked forward by the downward pull of the head. 
How the third spine is moved is not so clear. Dr. Grenacher suggests that it is 
dragged forward by the other two, which are often crossed beneath it; but adds that 
this is a forced explanation. It is probable, I think, that this spine is driven forward 
by the sudden jerk downwards on its base, when the longitudinal muscles sharply com- 
press the stiff ventral cuticle. Fine muscular fibres surround the trunk at regular 
