VERMES. 59 



Order I. HIRUDINEA. (Leeches.) 



DlSCOPHORA. SUCTORIA. 



Mostly aquatic animals, with a sucking-disk at one or both 

 extremities. Hermaphrodite. No metamorphosis. 



Although ringed, the body is not divided into distinct somites, 

 the rings being merely surface-markings. Respiration is effected 

 by the skin or by lateral sacs. The circulatory system consists 

 mostly of longitudinal trunks or a series of sinuses. The eyes 

 are little more than pigment-spots. The skin is without cilia. 



Leeches are mostly freshwater animals, swimming easily ; but 

 many are parasites on fishes, Mollusca, and Crustacea. A few are 

 terrestrial, occurring in Japan, Ceylon, Chili, &c. 



The ordinary leech is Hirudo medicinalis ; the Hungarian 

 leech (H. officinalis) is probably a variety. Horse-leech ia a name 

 given to two distinct species, or even genera Hcemopsis sanguined 

 and Aulostomum gulo. Macrobdella valdiviana is 2J feet long. 



Malacobdellidce. Clepsinidee. Trochetia. 



Malacobdella. Clepsine. Aulostomum. 



Piscicola = Ichthyo- Nepheks. 



Acanthobdellid<s. bdella. Hirudo (Leech). 



AcanthobdeUa. Haemopsis. 



Histriobdella. Hinidinida. Pontobdella (Sea- 



Branchiobddlide. 3 " Branchellion. 



Branchiobdella. Bdella. 



Order II. OLIGOCH^TA. 

 LUMBRICINA. TERRICOLA. SCOLEINA. ABRANCHIATA. 



Mostly land- or freshwater-worms, without feet, but provided 

 with bristles [setae]. Mouth rudimentary. No branchiae. 

 Mostly hermaphrodite. No metamorphosis. 



Reproduction is mostly by ova or by gemmation ; but the 

 earth-worm (Lumbricus terrestris) develops directly. Respira- 

 tion is by the skin. 



These worms are generally found in the mud of ponds and 

 streams ; they are never parasitic or inquiline. They have great 

 powers in repairing injuries. 



