176 ZOOLOGY. 
to Clymene, having been dredged by the Challenger Expedi- 
tion at the enormous depth of over three miles (about 5000 
metres). 
Cuass [IX.—ANNULATA. 
Body long, bilaterally symmetrical, cylindrical, consisting of numerous 
segments, either unarmed, or more usually provided with sete alone or with 
sete and paddle-like appendages (rami). Head simple, with a few simple 
eyes, or provided with tentacles (antenna) alone, or with tentacles and bran- 
chia. Aneversible pharyna, armed with teeth, usually present. Alimentary 
system straight, the tubular stomach sometimes sacculated ; vent always 
situated in the last segment of the body. Nervous system well developed, 
consisting of a brain and ventral ganglionated cord. Circulatory system 
closed, with a dorsal and ventral and lateral vessels connected by anasto-. 
mosing branches in nearly each segment. A system of numerous paired 
segmental organs, Sexes united or separate. Embryo passing through 
a cleawage-stage (morula or blastula), gastrula, sometimes a neurula stage, 
and after hatching, development is either direct or there is a marked met- 
amorphosis, the larva passing through a trochosphere and cephalula 
stage. 
Order 1. Hirudinea.—Body unarmed, finely segmented ; with a pos- 
terior sucker. (Hirudo, Nephelis.) 
Order 2. Annelides.—Suborder 1. Oligocheta (Lumbricus, Nais), Sub- 
order 2.—Chetopoda (Arenicola, Syllis, Autolytus, Aphro- 
dite, Polynoé, Amphitrite, Terebrella, Sabella, Serpula, 
Spirorbis). 
TABULAR VIEW OF THE CLASSES OF WorMs (VERMES). 
Annulata, 
Brachiopoda. 
Enteropneusta. ees Polyzoa. 
TOs 
as Rotatoria. 
| tasnie a Nematelminthes. 
ey ne 
| 
VERMEs, 
