Our Fresh-Water Planarice. 453 



* Intestine dendritically branched. 



Family I. — Planocerid^. Flat : the mouth nearly in the 

 centre of the ventral surface, and furnished with a short 

 proboscis, crenated or lobed at the orifice. 



1. — Leptoplana, Multocular, the eyes clustered : no 

 tentacula. 



2. — Eurylepta. Multocular, the eyes clustered : two frontal 

 tentacula. 



3. — Planocera. Multocular, or eyless : two dorsal tentacula. 



Family II. — PiANARiADiE. Flattish : the mouth inferior, 

 sub-central, with a long cylindrical proboscis, plain at the 

 orifice. 



4. — Poly celis. Eyes, many, in a marginal series. 



5. — Planaria. Eyes, two; dorsal and paired. 



** Intestine an undivided tube. 



Family III. — Dalyellim:. Mouth terminal, or sub-central, 

 eproboscidean. 



t Eyes, two. 



6. — Dalyellia. Mouth, terminal. 



7. — Derostoma. Mouth, ventral, anterior. 



8. — Mesostoma. Mouth, ventral, sub-central. 



J Eyeless. 



9. — Opistomum. Body, elongate; mouth terminal. 

 10. — Typhloplana. Body, linear-oblong : mouth ventral, 

 sub-central. 



11. — Gonvoluta. Body, involute. 



In the Planocerid.^, the body is thin, flat, and laterally 

 expanded ; the eyes when present, are clustered. _ The oral 

 aperture is usually closed, and becomes almost indistinguish- 

 able, but the position of it, and of the proboscis, is marked by 

 an oblong spot, near the middle of the ventral surface. This 

 is always paler than the dorsal, which is commonly beautifully 

 coloured. The motion is slow. The food is soft, either the 

 juices of invertebrate animals, or the parenchyma of decaying 

 algae. All are marine, and propagate, probably, by naked 

 cilated ova, undergoing no metamorphosis. In decay the body 

 is diffluent, and decomposition has far advanced before life 

 is extinguished. The species Leptoplana tremellaris and 

 Eurylepta vittata, with its sinuated margin, and dotted, 



