116 PLANARIA. 
In crawling up the side of a vessel, it is liable to drop to the bottom, 
but its descent seems to be retarded by an invisible thread. Marine. 
The specimen survived several weeks. 
Prats XVI. 
Fic. 20. Planaria variegata, enlarged. 
g-—PLANARIA ALBA.—Plate XVI. Figs. 21, 22. 
Length nearly three lines ; thickness the fifth or sixth of the length ; 
body roundish ; extremities obtuse ; anterior extremity the smallest. 
Two circular very black eyes, at about the fifth of the whole length, be- 
hind the anterior margin ; colour pure white ; motion smooth and gliding ; 
intestinal organ not pinnate. Marine. 
Pirate XVI. 
Fig. 21. Planaria alba, enlarged. 
22. Anterior portion, shewing the position of the eyes, enlarged. 
A.—PLANARIA GRACILIS—Slender Planaria.—Plate XVI. fig. 25. 
Length a third of a line ; body rather linear, flattened ; eyes two, 
black towards the upper surface ; mouth apparently below, under the 
eyes ; colour white ; motion swift, swimming through the water. Several 
specimens taken during June in Lochend. 
Puate XVI. 
Fig. 28. Planaria gracilis, magnified. 
?.—PLANARIA EXIGUA.—Plate XV. Figs. 15, 14. 
Length a third of a lime ; form a double cone when in motion ; two 
black eyes on the surface of the neck ; colour of some specimens reddish 
in the middle, and when crawling too near the edge of the water, they 
contract into a reddish spot and perish ; motion swift. A dark globular 
