ANTHOZOA HYDROIDA. §3 
general fleshy substance of the body. The growth of the 
polypidom is dependent on the growth of the pulp, or rather 
they grow together, as the feathers, beak, and claws increase 
in size on a young growing bird. 
Careful observations have been made on the polypidom, 
with its included pulpy matter, and the result is as follows. 
The ovule, when matured, drops from the vesicle, and fixes 
on some rock, or seaweed, or shell, or sometimes even on 
some other marine animal, such as an Ascidia. Minute 
fibres, proceeding from its under side, cause it to adhere, 
while from the upper side the commencement of the stem 
springs up. ‘The structure of this shoot is at first homo- 
geneous: gradually, however, the pulp is formed in the 
inner part, and the shoot, having assumed a bulbous form at 
the summit, condenses and expands, and so does the horny 
covering, till one or more closed cells are formed. By and 
by, little knobs protrude from the cells, and increase till 
they become tentacula, when the cell opens and the ani- 
mal begins to catch its prey; and from that moment it 
is as large as ever it is at any subsequent period. But 
though the polypes increase not in size, they increase in 
number ; for, as the newly-formed one is constantly obtain- 
ing nourishment, the central pulp increases and _ shoots. 
