118 BULLETIN : MUSEUM OF COMPARATIVE ZOÖLOGY. 
The cilia of the siphonoglyphes wave invariably inward. Possibly 
the stimulation of the siphonoglyphe surfaces by meat juice gives rise 
to a peristaltic movement in the gullet. 
The cilia of the lips usually wave outward. The direction of their 
stroke can be temporarily reversed by meat juice. Application of this 
to the lips calls forth peristaltio movements of the gullet. 
The contraction of the sphincter of the oral disk and the peristaltic 
movements of the gullet can be produced by stimulating with meat 
juice either the lips or the tentacles. To induce movements in the 
tentacles, meat juice must be applied directly to them. 
The effects of frequently repeated weak chemical stimuli on one side 
of the oral disk are not transmitted in any appreciable degree to the 
other side, i.e. the nervous functions are not centralized. 
In an expanded quiescent Metridium, the tentacles point away from 
the mouth and their cilia wave towards their tips; the cilia in the 
siphonoglyphe wave inward, those on the lips outward. If any indiffer- 
ent substance is dropped on these parts, it is carried along with the 
ciliary currents. If a piece of meat be placed on the tentacles, these 
turn their tips toward the mouth (muscular response), and their cilia 
carry the meat to their free ends, from which it drops on the lips. The 
cilia of the lips thereupon reverse, and the meat passes down the gullet, 
partly by ciliary action and partly by peristaltic movements (muscular 
response). 
CAMBRIDGE, January 6, 1896. 
