ANNULATA. 225 
Orpver II. Suetoria. 
Body annulate, without sete, terminated by a prehensile cavity 
posteriorly or at both extremities. External branchie none. 
Family III. Hirudinea. (The characters of the order are also 
those of the single family.) 
The family of the blood-suckers (leeches) is formed from the genus 
Hirudo L. These animals are able to convert the anterior extremity 
of the body into a suctorial cavity, or have there, as at the posterior 
extremity, a round suctorial disc. They creep along the ground, by 
affixing this sucking apparatus and by alternately contracting and 
extending the body. They swim with a serpentine and sinuous 
bending of the body, which is eifected with much velocity. 
Comp. on this family Moguin-Tannon, Monographie des Hirudinées, 
nour. Edit. av. pl. color. Paris, 1846, 8vo. 
A, Head made up of several segments of the body, slightly or 
not at all distinct from the rest of the body, capable of change into 
a suctorial acetabulum by its own motions. 
Clepsine Savy. Body depressed. Mouth unarmed, furnished 
with a proboscis exsertile, tubular. Eyes 2—6 (sometimes eight ?). 
Sp. Clepsine hyalina, Hirudo hyalina L., TrumBury, Polyp. Pl. vit. fig. 7 ; 
Clepsine complanata, &e. 
This animal lays its eggs on water-plants (Stratiotes aloides) and continues 
to sit thereon. The eggs also attain their development even when the mother 
is driven away, but are then frequently affected and spoilt by conferve. These 
eggs are thin-skinned vesicles in which numerous yelk-spheres, 15 to 30, 
are contained, and from which a corresponding number of young are 
developed. 
Comp. on the species of this genus F. Muntier, De Hirudinibus circa 
Berolinum hucusque observatis, Berolini, 1844, 8vo, and T, BupGE, Clepsine 
bioculata. Mit 2 Taf. Bonn, 1849. 
Under this genus F. MuELLER also places Hirudo marginata and Hir. 
tessulata of O. F. Mur.iEr, though the last has eight eyes, whilst in 
Clepsine the number does not exceed six ; the arrangement of the eyes is 
in two rows longitudinally which meet forwards, just as in the six-eyed 
Clepsines ; the blood also is white. 
Nephelis SAv. Body elongate, posteriorly incrassated, obtuse, 
with acetabulum obliquely terminal. Mouth unarmed. Eyes eight, 
disposed in a series semicircular, transverse. 
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