102 THE WORLD OF THE SEA. 
selves at the end of each canal; these are the embryos of the 
eyes. Gradually the bud assumes a bell-like form. Its mouth 
dilates, the four eyes separate, and from their vicinity four tentacles 
issue. The central reservoir increases, but it is limited and enclosed 
by a membrane, thus forming the stomach; now the animal is per- 
fect; it is a true medusa. Ina little time it will break its pedicle 
EXPANDED POLYPES. 
(Sertularia pumila.) 
by violent contractions and will swim out to the open sea. The 
young medusa, thus liberated, in a few days becomes double its size, 
and at the point where its pedicle separated from the parent stem, 
the tentacles elongate, and there a mouth appears. Ina few weeks 
the intestines of the young medusa increase in size. This is because 
eggs are being produced which gradually enlarge and at length 
separate themselves by a process similar to the one described. 
