316
TH. LENDER
inductive influence of a cephalic or prepharyngeal region and this could
occur even in the absence of a caudal bud.
We may, therefore, conclude with Wolff (1953) that the cephalic
region induces a pharyngeal zone which acquires the capacity of causing
the differentiation of the pharynx.
2. Differentiation of the Genital Organs
The regeneration of the genital apparatus and of the gonads has been
M.
a.
b.
N.
c.
Ovc.
d.
FIG. 7. Repair of an irradiated ovary. Top: Control ovary; oöcytes at the end of prophase or in metaphase, surrounded by young oöcytes and oögonia (Ovg.). Bottom: The
neoblasts (N) are transformed into oögonia (a), divide (b), and move (c) around the
irradiated oöcyte (Ovc.) to form young oöcytes (d). S: direction of migration; M: muscles;
C. par.: parenchymal cells. (Dubois, 1949, Fig. 37, p. 266.)