FIG. 23. Blastogenic zone of Cristatella mucedo with a primordial bud (B) and
secondary bud (C). Note the embryonic cells of the base of the ectoderm (C.B.)
which have produced, by proliferation, the inner layer of the buds and which migrate
in the axis of the funiculus (Fu.) to become the cyst precursor cells (Cy.) of the
future statoblasts. C.V.—vascular cells of the ectoderm; Pa.—parietoplura; M.C. and
M.L.—circular and longitudinal muscles of the wall.
reviewed is sufficient to show what differentiates ontogenesis of the
oozooid from that of the blastozooid zooecium. The bud is actually a
swelling of the wall of the parent zooecium. It becomes individualized
while growing to give rise directly to a cystid forming its polypidian bud.
Besides parietal or colonial budding, the phylactolaemate has budding
by dissemination. At the level of the funiculus it produces statoblasts—
BLASTOGENESIS AND MORPHOGENESIS
193