112 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
The reaction of the tentacles of Metridium to the soluble parts of the 
food is due in all probability to local stimulation, no tentacle moving 
until the soluble parts of the food have come in contact with it. This 
opinion is supported by what can be observed on tentacles which have 
been removed from the actinian, but which have been kept in such 
positions that their original orientation in reference to the animal can 
still be recognized. Such tentacles, when stimulated by meat juice, 
turn in a direction that indieates the original position of the mouth 
in reference to the given tentacle. We are therefore forced to admit 
that each tentacle has within itself a complete and independent nervous 
and muscular mechanism capable of carrying out normal responses. 
The Intermediate Zone, occupying the space between the tentacles and 
the lips, possesses no specially differentiated structures. 
When small particles of carmine are placed upon it, they remain 
stationary for some time, and then move slowly over the surface to the 
base 9f the tentacles, whence they are discharged from the disk, as already 
described. Pieces of crab meat are acted upon in much the same way, 
except that, when this material reaches the tentacles, these organs re- 
spond in their characteristic way, and transport the meat to the lips. 
That both carmine and small pieces of meat may remain motionless for 
some time on the intermediate zone indicates that this zone is not cili- 
ated, a conclusion supported by the fact that, when a portion of the zone 
of a living animal is examined under the microscope, no evidence of 
ciliary currents can be detected. The movements towards the base of 
the tentacles, which as a rule are finally shown by the carmine and 
pieces of meat, seem to be due to suction produced by the tentacular 
cilia, or to the entanglement of the carmine or meat in extensive shreds 
of mucus which are being drawn by the tentacular cilia over the inter- 
mediate zone. Although nearly all the evidence favors the idea that 
the intermediate zone is not ciliated, the rapidity with which particles 
are sometimes swept over it leads one to suspect that it may possess 
here and there patches of cilia. If there are any cilia on this zone, they 
must wave away from the lips and toward the tentacles, for in this 
region movements in other directions have never been observed. 
The intermediate zone is probably incapable of being stimulated chem- 
ically by food, etc., for, when meat juice, solutions of quinine, of picric 
acid, or of sugar are applied to it, no responses are given. 
The Lip Zone, the innermost of the three zones of the oral disk, is in 
several respects more complex than the other regions described. In 
typical specimens it consists of two swollen furrowed lips, one on either 
