96 ZOOLOGY. 



Class 1. Annelida. 



The Annelida or Choitopoda are generally 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 eases 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 

 afibrd a means of defence, and thev varv much in character, some beins 



•1111 ^ tj 1 f5 



simple, and otiiers barbed in a variety of ways, presenting uniform charactei-s 

 which are useful in classification, and must be studied by those who wish to 

 be M^ell 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 tliree 

 orders, named Abranchia, Dorsibranchia, and Tubicol.e : but as the 

 names of orders should be taken from the same part, the last one is here 

 replaced by the term Ckphalobrancuia.* 



Order 1. Abranchia. The animals of this order are without branchiae, 

 respiration being efl:ected by means of the skin. Cuvier supposed certain 

 lateral pores to be respirator}' orifices, but these have been ascertained to 

 be the outlets of the organs which supply the mucus. The order includes 

 the four families : Hirudinidm (leeches) ; LumbriGidm (earth-worms) ; 

 Echiuri I and Maldanioe. 



Fain. 1. Ilirudinidm. 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. Some species are cylindrical, and 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 eflected 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, larvae, 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. 

 300 



