100 ZOOLOGY, 
submerged stones, sticks, and leaves in ponds. The body 
is partly transparent, with a dark area representing the- 
stomach, from which branch out at right angles a multi-. 
tude of cecal canals (gastric ceca). It has two small. 
black eye-specks. Closely allied to this flat worm is an eye- 
less form inhabiting the streams of the Mammoth and ad- 
joining caves, which may be called Dendrocelum percwcum. 
(Fig. 64). 
The foregoing forms are easily obtained by the student, 
who can study their habits in confinement. They all be- 
long to the order Turbellaria, which is characterized by the 
flat, oval body, covered with cilia. The ciliary motion can. 
be detected, as Moseley has done, by placing a little arrow- 
root meal or fine bits of paper on the back of the animal ; 
these were seen to move in a forward direction on the an- 
terior part of the body of Geoplana flava Moseley, a Bra-. 
zilian land-planarian, and posteriorly they moved backward. 
‘*Tn all regions of the dorsal surface it moved outward, 
as was observed by Fritz Miller, at the same time as back-. 
ward or forward, and was thus rapidly thrown off at the 
side of the body, the dorsal cilia apparently subserving 
especially this function of the speedy removal of foreign 
substances from the surface of the body ’’ (Moseley). The 
structure of the flat worms may be understood by referring 
to Fig. 65, which illustrates the anatomy of a common 
European marine flat-worm. The digestive canal opens,by 
a mouth situated usually behind the middle of the body, 
which leads into a chamber containing a cylindrical or: 
funnel-shaped proboscis, capable of being suddenly thrust 
out. The digestive canal is either a short blind sac, or is. 
long, forked, and either simple or much branched (Fig. 
65, e). 
These worms have a so-called water-vascular system, con- 
sisting of two lateral canals and numerous branching lat-. 
eral stems, with a common opening or pore in the skin be- 
tween the two main stems, or there may be many pores. 
The vessels are ciliated within, and are supposed to have a. 
respiratory or excretory function. The nervous system con- 
sists of a double ganglion situated on the front end of the- 
