292 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
The lateral canals are two slender tubes, in some species considerably convo- 
luted, in others much less so, which begin in the anterior part oi' the body and run 
backward, one along each side, to the contractile vacuole. The lateral canal bears 
on each side four or five small evaginations, each containing a long cilinm; these 
are the so-called flame cells or vibratile tags (pi. n, fig. 24). 
The contractile vacuole (fig. 24, c. v.) is unusually small and inconspicuous in 
the Ratlulidce. It is a spherical vesicle lying just beneath or at the side of the 
intestine near its posterior end. It is situated above the large mucus reservoirs 
(to. r.), which are sometimes mistaken for the contractile vacuole. 
The contractile vacuole usually pulsates rather rapidly, perhaps in consequence 
of its small size. Twenty times per minute seems a not uncommon rate; in Diurella 
brachyura Gosse, according to Stokes (1896), there are 40 pulsations per minute. 
The contractile vacuole in most rotifers opens into the intestine near its posterior 
end; this matter has not been especially investigated in the Rattulidce,. 
(4) Reproductive organs. — The male seems to be quite unknown in the Rat- 
tul idee. No member of this family is given in Mr. Charles Rousselet’s list of male 
rotifers hitherto described (1897), and I have myself seen nothing of a male in any 
of the species studied. 
The ovary (ov.) is an irregular, frequently somewhat lobular, organ, differing 
in no important manner from the same organ in most of the related free-swimming 
rotifers. As Plate (1886) has shown, the ovary in most of the Rotatoria consists of 
two parts, a vitelline portion (“ Dotterstock ”) and a germinal portion (“ Keimstock ”). 
The latter is smaller than the former; from it the eggs are directly produced. The 
germinal portion seems to lie at the right side or right anterior corner of the 
vitelline portion, in the Rattulidce .. The vitelline portion contains a small number 
(usually if not always eight, in this family) of large, conspicuous nuclei. 
The ovary lies on the ventral side of the alimentary canal, usually mostly to the 
left of the median line. In Rattidus latus Jennings (pi. vn, fig. 65) it lies entirely to 
the left of the alimentary canal, not on the ventral side of the latter at all. 
The eggs are formed in the germinal portion, to the right of the main body of 
the ovary. When the egg has reached a considerable size, it usually occupies a large 
space on the right side of the body, as in fig. 32 (pi. in). 
In the Rattulidce , so far as known, the egg, after extrusion, is carried attached 
to the lorica in only one species, Rattidus cylindricus Imhof. In this case the ani- 
mal is frequently found carrying the egg attached to the posterior end of the lorica, 
above the foot (pi. vn, fig. 62). 
(5) Mucus glands and reservoirs. — The glands and reservoirs for supplying the 
tenacious mucus-like substance, by which the animals attach themselves to various 
objects, are unusually well developed in the Rattulidce. The reservoirs especially 
form a large, clear, oval sac, or a pair of sacs, filling a considerable part of the hinder 
portion of the body. There are typically two of the glands and two of the reservoirs 
in the Rattulidce. They are well shown in fig. 92 (pi. x); fig. 79 (pi. ix), and fig. 69 
(pi. viii). The two glands are rounded or irregular granular bodies, lying near the 
ventral surface, just behind the ovary. 
The two reservoirs are usually pressed close together or even united, so that it 
is perhaps just as correct to speak of a single reservoir divided into two chambers 
by a longitudinal partition, as of two reservoirs. Into these chambers passes the 
secretion from the glands; it may often be found in preserved specimens as a solid 
