ARTICULATA. 271 
limbs, and by the fact that no one part of the body is 
highly honored above the rest. The body is soft, and 
composed of a succession of rings (from 20 to 500), which 
are repetitions of each other. The first segment, called 
the head, differs little from the rest. The legs, when ex- 
isting, are merely bunches of short, stiff bristles (sete), 
each terminating in a hook or blade. Many of the sea- 
worms have tentacles. ‘Touch is probably the only sense. 
iD si) M ‘\ y 
sy tt mS 
ap Ou 
Fig. 243. — Rotifer, or 
‘**Wheel-animalcule” 
Fig. 242,—Tape-worm (Tenia soliwm): a, head; B, ec, (Hydatina); highly 
d, segments of the body. magnified. 
The blood is often reddish, but seldom contains corpus- 
cles. Strange to say, the circulatory apparatus is closed, 
and more highly developed than in Insects. They are 
mostly marine, and carnivorous. 
There are three representative orders: 1. The low and 
abnormal Annuloida, which are without joints or sete, 
and are mainly parasitic, as the Tape-worm (Zenza), 
Hair-worm (Gordiacea), and Trichina.'” 2. The Abran- 
