I9I4- Whitehouse. — The Nattiral History of Planariam. 43 
the general body tissues ; this species is indeed a giant 
among the freshwater planarians, specimens often measuring 
over an inch ; another species common in the streams 
on Cave Hill is Planaria alpina, a small animal with lappets 
at the sides of the head ; it is found in large numbers 
on the under side of stones soon after the stream issues 
from the chalk. Beauty of colour is at its height among 
the tropical land planarians ; selections from black, white, 
purple, blue, green, yellow, red, etc., are productive of 
exquisitely beautiful forms. The commonest arrangement 
is the stripe, either longitudinally along the animal or cross- 
wise ; sometimes marbled or speckled patterns are shown, 
while others are unicoloured Almost invariably the under 
surface is paler than the upper, probably because the varied 
colouring of the upper surface is not needed on the parts 
not exposed to the passers-by. The brilliant colouration 
of land -planarians must be looked upon as a warning to 
animals likely to prey upon worms ; from experiments 
with birds they have been shown to be distinctly distasteful, 
and Prof. Dendy tells us that he has himself tasted them, 
and found them very disagreeable ! 
The characteristic mode of movement among planarians 
is by means of short and indefiniteh^ numerous hairlike 
piocesses called cilia. The planarian does not come into 
actual contact with the surface over which it glides, but 
lays down a mucus, just as a snail does, and it is on the 
smooth surface of its own mucus or slime that it moves ; 
the slime is produced by glands distributed all over the 
lower surface, particularly at the edges. Except for the 
head itself, the whole of the lower surface is in contact with 
the slime-covered substratum as the animal moves. The 
uninitiated person nearly always refers to planarians as 
leeches, but this mistake would never be made if the 
method of locomotion were observed ; a leech moves by 
looping with the aid of a sucker at each end of the body ; 
a planarian glides. 
The planarian holds its head up in the world ; the 
anterior end is always slightly raised and waved from side 
to side ; at the same time the exceedingly mobile and 
