190 ANNULATA. 
ARENICOLA. 
SEGMENTS, APPENDAGES, Beene Pees APERTURES, GILLS, 
Prostomium. Brain. Mouth. 
Peristomium1 Nerve ring. Otocyst. 
2| Parapodia. 
"W 
" Nephridium | Nephridio- 
5 " a 2 pore I 
6 " " 3 1 2 
7: " " 4 " 3 
8 " " 5 " 4 |Gillr 
9 " 1 « 6 " 5 rae 
sfe) " uM! 6 n 3 
II " u 4 
12 " Nerve cord. u 5 
13 ty u 6 
14 " "7 
15 an n 8 
16 " u 9 
17 " i ce) 
18 " wiI 
19 tt uwiI2 
20 " uI3 
Tail, &c. Anus. 
III.—HIRUDO. 
PHYLUM - ANNULATA (p. 237). 
Sus-PHYLUM ANNELIDA (p: 238). 
Crass - HIRUDINEA (p. 239). 
Fig. 116.—THE MEDICINAL LEECH 
(Hirudo medicinalis ), 
The more tapering end is anterior. The centre, individual 
is seen in the action of swimming. 
