SEVENTH BRANCH OF ZOOLOGY. 



HELMINTHOLOGY. (Gr. "e^s* helmins, a worm ; ioyo ff , 

 a discourse.) 



Class ANNELIDANS or WORMS. 



This lowest division of the ARTICULATES is arranged by Cu- 

 vier and other naturalists, into two sections ; the one embracing 

 the class Annelidans, or Red-blooded Worms, and ranked with 

 the Articulates ; the other, including the Intestinal or White- 

 blooded Worms, is ranked by them with the Radiates. Agassiz 

 considers the nervous system of the latter Worms, which has 

 been made a ground of their separation, though somewhat differ- 

 ent, as yet essentially the same with that of the Articulates. 

 We follow him as well as other distinguished naturalists, in 

 placing all the Worms in this latter class. 



FIRST DIVISION. ANNELIDA, (Lat. annulus, a ring.) RED- 

 BLOODED 'WORMS. 



These always have their bodies formed of a great number of 

 small rings nearly equal in size, varying in number from twenty 

 or thirty to more than five hundred, according to the length of 

 the animals. Their skin is soft and pliable ; and their bodies, 

 not having any external skeleton, are also soft, and in general 

 more or less cylindrical. The head is usually distinct, furnished 

 with two or four eyes ; the sides have attached to them feet, or 

 rather bristle-like projections, which are used for locomotion, and 

 vary widely in different species. Most of the anneiidans are 

 marine ; but some live in fresh water. 



