55 
segments. There is a similar variety in the internal 
anatomy of the different divisions of worms, the 
lowest of which sink to a very degraded stage. 
Many worms pass a free life in damp ground, or in 
Class’ 1. 
We place the Wheel Animalcule first, because 
they exhibit so many affinities to other Classes. 
They are almost microscopic organisms (the largest 
are ‘50 of an inch in diameter) and are mostly in- 
habitants of fresh water. They have a ciliated appa- 
ratus on the upper part of the body which has the 
appearance of revolving wheels. The living animals 
are perfectly transparent, and are charming objects 
under the microscope, and very easy of observation. 
Some swim freely about, and others are sedentary 
in their habits. 
| 
| 

salt or fresh water, but an equally large number are 
parasitic on other animals, among which are the 
best-known and most dangerous parasites of man. 
Rotatoria. 
Fig. a. Rotifer vulgaris has a crown of two 
ciliated wheels, and two eye-specks on the proboscis. 
At the back of the neck is a sucking-tube. The 
forked foot divides twice. The parts of the body 
indicated in the figures are as follows: 1) Eye- 
specks; 2) Wheels, exserted & retracted; 3) Sucking- 
tube; 4) Jaws, almost always employed in mastication; 
5) Glands; 6) Stomach; 7) Termination of intestine; 
8) Cells surrounding the stomach (liver-cells); 9 and 
10) Eggs, one containing an embryo; 11) retractile 
foot. 
Annelida. 
These animals are the highest of the worms, | wiSe they breathe, as is usual in the class of worms, 
Class. II. 
and are characterised by their bodies being divided | with the whole surface of their bodies. 
into a consecutive series of similar parts (rings or 
segments). They always possess blood-vessels and 
a nervous system, with organs of sense, but the 
development of special organs of respiration is only 
found in the most highly developed species; other- 
Order I. 
These worms are provided with bristles on the 
various segments of their body, which differ in 
shape and size, and are sometimes so abundant that 
they cover the animal with a thick downy clothing, 
and give some of the marine species a metallic lustre 
comparable to that of birds and insects, though most 
of the Chetopoda are dull and uniform enough in 
colour. 
Section I. Polychietie. 
Worms provided with tentacles, cirrhi, and gills. 
The numerous bristles are situated on the rudiments 
of legs. They undergo metamorphoses. 
Fig. b. Aphrodite aculeata, the Sea-mouse, is 
a common marine species thickly clothed with iri- 
descent hair. Like most of its allies, it is a decidedly 
carnivorous animal. 
Fig. c. Folynoe impatiens is a similarly irides- 
cent species. 
Fig. d. Nerets margaritacea is a slender species, 
capable of very rapid movement. It has several pairs 
of tentacles, and four eyes, as well as two strong 
pincerlike jaws, besides smaller teeth for tearing 
its prey. 
The large number of allied marine forms are 
classified by the structure of the mouth-parts, and 
the form and number of their bristles. We have 
figured two more species of this division, CLove lucida 
(fig. e) and Szphostoma diplochetos (fig. f). 
Fig. ¢. The Lug-worm (Arenzcola piscatorum) 
varies a little in colour, and grows to the length of 
ten inches. Its body is divided into three sections, 
of which the middle one bears most appendages, 
and the hindmost none at all. The Lug-worm lives 
in the sand between tide-marks in the manner of 

A few of 
these animals are casual parasites, but most live free. 
According to their external appearance, they may 
be easily divided into two suborders, the Worms 
and the Leeches. 
Cheetopoda. 
earthworms, and is very abundant in many places. 
{t is much used by fishermen for bait. 
With the Lug-worm we commence the section 
of Chetopoda which construct a tube-like dwelling, 
partly from materials which they find on the sea-bed, 
and partly derived from their own organisms. Another 
illustration is the following : 
Fig. h. Serpula contortuplicata is a handsome 
species belonging to a large genus which covers any 
object which lies long in the sea with irregular tub- 
ing. They expand a beautiful crest of tentacles, but 
dart back into their tubes, the instant they are alarmed. 
These tentacles represent the gills, and between them 
rises a calcareous lid which closes the tube. The 
mouth exhibits neither proboscis nor teeth. 
Section Il, Oligochietie. 
In these worms, tentacles, gills, mouth-armature 
and rudiments of legs are absent. The whole structure 
is inferior to that of the Polychete, and the bristles 
are small and scattered. The animals are herma- 
phrodite, and the eggs are laid in capsules, from 
which the young are developed without undergoing 
any metamorphosis. 
Fig. i. Lumbricus terrestris is one of the 
earth-worms which live in mould, feed on the rotting 
substances which it contains, and reject what they 
cannot digest. Darwin has demonstrated their great 
importance in the economy of nature. 
Fig. k. Nads proboscidea is a fresh-water worm 
with but few bristles. It is common in ditches and 
ponds, and is a transparent creature with a proboscis- 
like sucking-tube on the head, and two rows of 
hooked bristles on the belly, as well as a row of 
straight hairs on each side. 
