BLASTOGENESIS AND MORPHOGENESIS
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tached to the parent zooid and will form its pygidium; the b part will
develop into the head region and anterior portion of the blastozooid, thus
becoming a part of it. After scissiparity, the worm is reconstituted, and
elongates by proliferation of its pygidial region, a.
Precocious scissiparity, an accelerated form, appears after and is
added to the slow form. The process can be continuous (Figs. 6 and 7).
FIG. 7. Nais variabilis. Precocious scissiparity (Sc. h.) in segment N, followed by
precocious scissiparity (Sc. h.). The former isolates the blastozooid Z.l from the
parent zooid; the latter separates the blastozooid Z.2 formed by segment N, constructed from the anterior region of the original segment after the first scissiparity
had occurred, (After L, Dehorne.)
161
tached to the parent zooid and will form its pygidium; the b part will
develop into the head region and anterior portion of the blastozooid, thus
becoming a part of it. After scissiparity, the worm is reconstituted, and
elongates by proliferation of its pygidial region, a.
Precocious scissiparity, an accelerated form, appears after and is
added to the slow form. The process can be continuous (Figs. 6 and 7).
FIG. 7. Nais variabilis. Precocious scissiparity (Sc. h.) in segment N, followed by
precocious scissiparity (Sc. h.). The former isolates the blastozooid Z.l from the
parent zooid; the latter separates the blastozooid Z.2 formed by segment N, constructed from the anterior region of the original segment after the first scissiparity
had occurred, (After L, Dehorne.)