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H E N R I E T T E HERLANT-MEEWIS
substances from these cells (Michon, 1962). This would explain the
earlier observations of Abeloos and Avel (1928), and recently confirmed
by Michon (1959), Saussey (1960), and Gallissian (1963), according to
which caudal regeneration in some Oligochaetae is possible only during
diapause. Saussey (1963b) has recently shown that a mere transection
of Allolobophora icteria during sexual activity, although kept in natural
summer conditions in a moist medium, is sufficient to promote diapause
followed by caudal regeneration 3 weeks later. Saussey (1960) and
Gallissian (1963) have also shown that removal of the brain or of the
anterior region of the nerve cord is followed by a pseudodiapause in the
course of which regeneration takes place. These diapause phenomena
are especially characterized by a nutritional interruption. We have been
able to observe many times that when traumatized the animal immediately ceases to take in food. At the same time, reproductive processes
are interrupted—ovulation stops and the genital organs begin to regress
(Herlant-Meewis, 1962).
We are not convinced that the hormonal phenomena involved in these
processes originate only in the brain, we are more inclined to regard
them as the consequence of activity in ganglion of the nerve cord. These
ganglionic neurosecretory cells are of importance for several invertebrate
groups (Gersch, 1959) and many annelids have been shown to contain
them. We ourselves have isolated four kinds of cells in Eisenia foetida
(Herlant-Meewis and Van Damme, 1962a, b), and at present we are
studying them systematically. We have already observed that, when
ovulation is interrupted following a period of fasting, these changes take
place in these cells; some seem to be in a resting stage while others
become particularly active. Regenerative capacity might be linked with
this activity. It seems probable that sexual reproduction and regeneration depend on the activity of two distinct types of neurosecretory cells
in the ventral ganglia that cannot function at the same time, one
suppressing activity in the other. This could be one reason for the
antagonism often noted between sexuality and regeneration in worms
and also for the interruption of asexual reproduction when sexual
activity begins in forms with both types of reproduction.
Neurosecretory phenomena could also explain the observations made
by Durchon and Marcel (1962) on the release of hormones favourable to
regeneration when the nervous system is transected in any region. In
fact, we have shown (Herlant-Meewis, 1961) in Eisenia foetida that
following ablation of some of the ganglia, an elaborative hyperactivity
manifests itself at the level of the neurosecretory cells in the remaining
ganglia. Secretory substances accumulate in the cells and their axons
during repair of the nervous centres and circulatory system and are then
discharged freely into the circulation.
H E N R I E T T E HERLANT-MEEWIS
substances from these cells (Michon, 1962). This would explain the
earlier observations of Abeloos and Avel (1928), and recently confirmed
by Michon (1959), Saussey (1960), and Gallissian (1963), according to
which caudal regeneration in some Oligochaetae is possible only during
diapause. Saussey (1963b) has recently shown that a mere transection
of Allolobophora icteria during sexual activity, although kept in natural
summer conditions in a moist medium, is sufficient to promote diapause
followed by caudal regeneration 3 weeks later. Saussey (1960) and
Gallissian (1963) have also shown that removal of the brain or of the
anterior region of the nerve cord is followed by a pseudodiapause in the
course of which regeneration takes place. These diapause phenomena
are especially characterized by a nutritional interruption. We have been
able to observe many times that when traumatized the animal immediately ceases to take in food. At the same time, reproductive processes
are interrupted—ovulation stops and the genital organs begin to regress
(Herlant-Meewis, 1962).
We are not convinced that the hormonal phenomena involved in these
processes originate only in the brain, we are more inclined to regard
them as the consequence of activity in ganglion of the nerve cord. These
ganglionic neurosecretory cells are of importance for several invertebrate
groups (Gersch, 1959) and many annelids have been shown to contain
them. We ourselves have isolated four kinds of cells in Eisenia foetida
(Herlant-Meewis and Van Damme, 1962a, b), and at present we are
studying them systematically. We have already observed that, when
ovulation is interrupted following a period of fasting, these changes take
place in these cells; some seem to be in a resting stage while others
become particularly active. Regenerative capacity might be linked with
this activity. It seems probable that sexual reproduction and regeneration depend on the activity of two distinct types of neurosecretory cells
in the ventral ganglia that cannot function at the same time, one
suppressing activity in the other. This could be one reason for the
antagonism often noted between sexuality and regeneration in worms
and also for the interruption of asexual reproduction when sexual
activity begins in forms with both types of reproduction.
Neurosecretory phenomena could also explain the observations made
by Durchon and Marcel (1962) on the release of hormones favourable to
regeneration when the nervous system is transected in any region. In
fact, we have shown (Herlant-Meewis, 1961) in Eisenia foetida that
following ablation of some of the ganglia, an elaborative hyperactivity
manifests itself at the level of the neurosecretory cells in the remaining
ganglia. Secretory substances accumulate in the cells and their axons
during repair of the nervous centres and circulatory system and are then
discharged freely into the circulation.