THE COMMON BED WORM OF OUR RIVERS. 11 
may be the means of inducing many such persons to examine 
and confirm our statements concerning its anatomy. 
Tubifex rivulorum (the River Tubifex), for so it has been 
called by the eminent naturalist Lamarck, belongs to the family 
of Lumbricidse, or Earthworms ; and the sub-family Naiadidae, 
or water-worms, according to some naturalists (for they burrow 
in the mud of rivers), whilst others rank it amongst the “ Seti- 
gerse,” or bristled worms (in consequence of its being furnished 
with two lateral rows of bristles), but in the same group, Lum- 
briciclae or Lumbricini. However we need not discuss this 
question with our differing authorities ; but may just observe 
that Tubifex is a genus of Annelides, allied to the Earthworm, 
having the rings indistinctly marked, and that it forms one of 
a group of fresh- water worms which burrow in the mud of rivers 
and ponds. It is from half an inch to an inch and a half long 
(Plate III. fig. 13), and is attenuated at each end. 
Owing to its various modes of reproduction it increases very 
rapidly, and its numbers cause patches of red on the surface of 
the mud on which it burrows, for half the bodies of the worms 
are protruded (fig. 12), the other half remaining in the ground. 
When the worms are disturbed, they withdraw them bodies, and 
then “ the red patches instantly disappear, from the retraction of 
the animals.”* 
With the aid of the lens, its “ annulose,” or ringed character, 
is revealed, but, as just stated, not so clearly as in the earthworm. 
Our figure (1) represents a magnified view of the animal, and 
from this it will be seen how clearly the internal organs are 
visible. These we shall now proceed briefly to describe. 
First we have along the whole length of the body the diges- 
tive canal (fig. 1, a), a dark tubiform organ, and attached to it 
(fig. 1, b), the dorsal blood-vessel of a deep red coloim. Ex- 
tending from the eighth to the sixteenth ring we find 'a white 
semi-opaque mass, comprising the organs of reproduction, which 
are of a very interesting nature, for we here find, as in many 
allied forms, both the male and female united in one individual. 
In connection with the red dorsal vessel are two hearts, if we 
may so term them (fig. 1, cl), which impel the blood through the 
numerous blood-vessels, of which the rhythmical dilatations and 
contractions are clearly distinguishable. 
We have already remarked that the external envelope of 
Tubifex is transparent. Let us now add that it consists of two 
layers, namely, a very thin “ epidermis ” or outer integument, 
and an internal skin or “ chorion,” which is intimately connected 
with the muscular membrane lying underneath the skin. The 
* Griffith & Henfrey’s Microscopic Dictionary (Van Voorst), article 
“ Tubifex.” Here also will be found the Bibliography. 
