STAR-FISH AND SEA-URCHINS, 257 
find that the central mouth leads by a short ceso- 
phagus into a central stomach, and that this in turn 
communicates with the intestine, which terminates 
in an orifice on the dorsal surface. Springing 
from the intestine at its origin, there are five tubes, 
each of which divides into two, and the five pairs 
of tubes thus formed extend into the five rays; 
Fig. 34.—Lower surface of common Star-fish. 
‘numerous blind processes grow out from these tubes, 
and give rise to glandular structures, which pro- 
bably perform the functions of a liver. 
When a section is made across the base of one of 
the arms, the furrows or grooves before mentioned 
are seen to be formed of two rows of plates con- 
