170
HENRIETTE HERLANT-MEEWIS
it to be a growth substance. There is no corresponding body in the hind
region of intact animals, but one is formed during pygidial regeneration.
Immediately after transection, chloragogue cells in adjacent segments
split up and congregate in the healing zone. Some of them completely
disintegrate, immediately releasing their storage products. Other cells
form an aggregate in the regeneration bud but in appearance they differ
from the typical eleocytes of the cephalic region. The nucleus is irregular
in shape and the cytoplasm becomes very pale ; granulations are more
frequently found at the periphery (Fig. 12, T). According to Liebmann,
the role played by these two types of trephocytes explains the mutual
independence of the two types of restitution and the different modes of
anterior and posterior regeneration under various conditions. Head regeneration is dependent on a constant factor, 'the presence of a cephalic
aggregate', it can take place throughout the region where this aggregate
is found and will be independent of sexuality, starvation and the
presence of a posterior regeneration bud. In the absence of eleocytes,
anterior regeneration does not take place; in Eisenia, for example,
anterior regeneration cannot take place if the worm is transected
posterior to segment 20. Regeneration will also be inhibited if the worm
is subjected to the effects of ether which causes the eleocytes to be
ejected through the dorsal pores. Caudal regeneration is controlled by the
release of chloragogue cells which normally act as nutritive elements for
sexual cells ; in consequence caudal regeneration may be incomplete or
even totally inhibited during the sexual period (Liebmann, 1942a, b).
Starvation reduces the number of chloragogue cells; if an animal is
deprived of food or is anteriorly transected so that it is incapable of
feeding itself, posterior regeneration is incomplete. Liebmann's theory
on trephocytosis explains the distribution of regenerative power along
the antero-posterior axis as well as polarity phenomena.
This conception of the origin and role of eleocytes is not in good
agreement with recent observations of Semal-Van Gänsen (1956) and
Van Gänsen (1963) on chloragogue cells in Lumbricidae. There the cells
contain reserve metabolites, glycogen and fats and certain complex
organelles—the chloragosomes which are calculi composed of chromolipids, heteroxanthin and muscovite. Thus the chloragogue wall of the
oligochaetes serves the dual purpose of liver and kidney in the sense that
waste products are accumulated. According to Semal-Van Gänsen, the
release chloragogue cells is not a process intended for trophic metabolism,
but for excretion ; the cells which are set free are waste elements which,
in the coelom, are soon surrounded by amoebocytes and destroyed.
Neither the role nor the origin of the different coelomic elements are as
yet well understood. Each of the peritoneal layers investing the various
organs has in turn been considered to be a generative tissue. Several
HENRIETTE HERLANT-MEEWIS
it to be a growth substance. There is no corresponding body in the hind
region of intact animals, but one is formed during pygidial regeneration.
Immediately after transection, chloragogue cells in adjacent segments
split up and congregate in the healing zone. Some of them completely
disintegrate, immediately releasing their storage products. Other cells
form an aggregate in the regeneration bud but in appearance they differ
from the typical eleocytes of the cephalic region. The nucleus is irregular
in shape and the cytoplasm becomes very pale ; granulations are more
frequently found at the periphery (Fig. 12, T). According to Liebmann,
the role played by these two types of trephocytes explains the mutual
independence of the two types of restitution and the different modes of
anterior and posterior regeneration under various conditions. Head regeneration is dependent on a constant factor, 'the presence of a cephalic
aggregate', it can take place throughout the region where this aggregate
is found and will be independent of sexuality, starvation and the
presence of a posterior regeneration bud. In the absence of eleocytes,
anterior regeneration does not take place; in Eisenia, for example,
anterior regeneration cannot take place if the worm is transected
posterior to segment 20. Regeneration will also be inhibited if the worm
is subjected to the effects of ether which causes the eleocytes to be
ejected through the dorsal pores. Caudal regeneration is controlled by the
release of chloragogue cells which normally act as nutritive elements for
sexual cells ; in consequence caudal regeneration may be incomplete or
even totally inhibited during the sexual period (Liebmann, 1942a, b).
Starvation reduces the number of chloragogue cells; if an animal is
deprived of food or is anteriorly transected so that it is incapable of
feeding itself, posterior regeneration is incomplete. Liebmann's theory
on trephocytosis explains the distribution of regenerative power along
the antero-posterior axis as well as polarity phenomena.
This conception of the origin and role of eleocytes is not in good
agreement with recent observations of Semal-Van Gänsen (1956) and
Van Gänsen (1963) on chloragogue cells in Lumbricidae. There the cells
contain reserve metabolites, glycogen and fats and certain complex
organelles—the chloragosomes which are calculi composed of chromolipids, heteroxanthin and muscovite. Thus the chloragogue wall of the
oligochaetes serves the dual purpose of liver and kidney in the sense that
waste products are accumulated. According to Semal-Van Gänsen, the
release chloragogue cells is not a process intended for trophic metabolism,
but for excretion ; the cells which are set free are waste elements which,
in the coelom, are soon surrounded by amoebocytes and destroyed.
Neither the role nor the origin of the different coelomic elements are as
yet well understood. Each of the peritoneal layers investing the various
organs has in turn been considered to be a generative tissue. Several