245 ZOOLOGY 
The group of mollusks represented by Ciiton (Fig. 202, 
Chiton ruber) have been referred to the worms by Jhering, 
_ on account of the segmented appearance 
of the plated shell, and the nervous sys- 
tem, which consists of two parallel: 
cords, connected by several commis- 
sures ;* as well as from the fact that the 
intestine ends at the hinder end of the 
body. The young 
is oval when hatch- 
ed, and is a trocho- 
sphere, haying a 
ciliated ring in the 
Fig. 200.—Slug. Nat- middle of the body 
wees with a long tuft of 
large cilia on the head. Afterwards 
it becomes segmented, as in Fig. 203, 
and is remarkably worm-like, the 
limestone plates of the adult’ corre- 
sponding to the primitive larval rings, 
Certain Gastropods are useful either 
as food or in the arts. In Europe 
Littorina littorea, the limpet (Patella of Penal’ c eyes op optic 
.vulgata), the whelk (Buceinum wn- ves % olfactory nerves. 
datum), and the Roman snail (Helix 
pomatia) are eaten. The sea-ear 
’ (Haliotis) is roasted in the shell. 
{itm The animal of’ Cymba, Strombus gi- 
(NS gas, Turbo, Trochus, and Conus are 
eaten in the tropics, while many of 
ASHE the larger forms are used for fish- 
bait. Pearls are sometimes found in 
Fie, 203. the species of Haliotis and Turbo. 
Fig. 202.—Chiton ruber. i is jf 
Fie BR 2 Bosmentoll larva The beautiful shell of Cassis is made 
of Chiton. into cameo pins, and the shell of 
Strombus gigas is in the West Indies made into ornaments. 
*In Fissurella and Haliotis the two nerve-cords from the pedal gan- 
glia are also united by nine transverse commissures, so that here also 
we have an approach to the double ganglionated cord of worms. 
