96 ZOOLOGY. 
Class 1. Annelida. 
The Annelida or Chetopoda are generaily recognisable by a soft body, a 
lengthened annulated form, red blood, and the nervous system central, 
ganglionic, and distinct. The rings of the body are of a membranous 
consistency, and never corneous as in insects, or calcareous as in the 
Crustacea. They are generally numerous, the length of the animal depending 
to some extent upon the number of rings, which vary from twenty or thirty 
to more than five hundred. When very numerous, the number is not 
uniform in the same species. ‘The head is usually distinct, and often 
provided with two or four eyes, and in some cases with a variable number 
of tentacles and cirri, but the last are not confined to the head. The sides 
are generally furnished with bunches of bristles and fleshy projections 
arranged in a line and used in locomotion; and although they are called 
feet, articulate limbs are never present. The lateral bristles in some cases 
afford a means of defence, and they vary much in character, some being 
simple, and others barbed in a variety of ways, presenting uniform characters 
which are useful in classification, and must be studied by those who wish to 
be well acquainted with the class. Their forms have been classified and 
named by Savigny. The alimentary canal is complete, extending from end 
to end. Most of the annelida are marine, some being free, whilst others 
‘construct a tube of calcareous matter, and of agglutinated particles of sand, 
fragments of shells, or other objects. Cuvier divides the class into three 
orders, named Asrancuta, Dorsrprancuta, and Tusicor#; but as the 
names of orders should be taken from the same part, the last one is here 
replaced by the term CrepHALOBRANCHIA.* 
Orpver 1. Aprancura. The animals of this order are without branchiz, 
respiration being effected by means of the skin. Cuvier supposed certain 
lateral pores to be respiratory orifices, but these have been ascertained to 
be the outlets of the organs which supply the mucus. The order includes 
the four families: Mirudinide (leeches); Lumbricide (earth-worms) ; 
Lichiuri ; and Maldanie. | 
Fam.1. Hirudinide. This family includes the worms known as leeches, 
- of which there are various genera, both marine and freshwater. The body 
is slimy and extensible, narrowing towards each end, composed of from 18 
to 140 segments. ae species are cylindrical, a others flattened, and 
the posterior extremity has a disciform sucker to enable the animal to 
adhere. In some cases the mouth is surrounded with a sucker also, and in 
these, besides swimming, locomotion is effected by extending the body, 
fastening the anterior extremity, and then drawing up the posterior one. 
The eye-like points vary in number from two to ten. The species feed 
upon blood or the juices of animal matter. Some have teeth to puncture 
the integument, but others, not being thus armed, attack only the softer kinds 
of food, as worms, larvee, or mollusca; and some swallow worms entire. 
* Some authors use the final syllable a, and some ata, in words like these, and as either form 
is correct, the shortest one may be deemed the best. 
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