In one zoophyte the head itself
was fixed, but the lower jaw free: in another it was replaced by a
triangular hood, with a beautifully-fitted trap-door, which
evidently answered to the lower mandible. In the greater number of
species, each cell was provided with one head, but in others each
cell had two.
The young cells at the end of the branches of these corallines
contain quite immature polypi, yet the vulture-heads attached to
them, though small, are in every respect perfect. When the polypus
was removed by a needle from any of the cells, these organs did not
appear in the least affected. When one of the vulture-like heads
was cut off from the cell, the lower mandible retained its power of
opening and closing. Perhaps the most singular part of their
structure is, that when there were more than two rows of cells on a
branch, the central cells were furnished with these appendages, of
only one-fourth the size of the outside ones. Their movements
varied according to the species; but in some I never saw the least
motion; while others, with the lower mandible generally wide open,
oscillated backwards and forwards at the rate of about five seconds
each turn; others moved rapidly and by starts.
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