REGENERATION IN ANNELIDS
203
exerted by a normal, non-amputated worm; hormonal storage in the
brain seems to have been triggered off simply by transection of the
peripheral nerve fibres at the point of implant.
To conclude, in Polychaetae, it seems that the brain must be present
at the time of posterior transection for regeneration to take place; transection itself triggers off endocrine activity of the cerebral ganglia.
In Oligochaetae, the facts are far from being so well established.
Hubl (1956), experimenting with Eisenia foetida and Allolobophora,
showed that if the supra-oesophageal ganglia were removed at the same
time as posterior amputation was carried out, the capacity for caudal
regeneration was completely inhibited ; on the other hand, if the brain
was removed 1 or 2 days after transection, the posterior segment was
reconstructed normally. He concluded that endocrine function in the
brain was triggered off by transection and that the hormonal discharge
was immediate.
Saussey (1961, 1962) obtained the opposite results with Allolobophora
icteria. He extracted the cerebral ganglia or nervous ganglia up to the
sixth segment in worms during the clitellar phase and simultaneously
cut through the middle of the body; posterior regeneration was much
more rapid in denervated worms than in controls. The rate of reconstruction was directly related to the importance of the part of the nervous system removed. In the species Saussey studied, ganglion extraction
stimulated diapause, a period particularly favourable to regeneration.
Saussey's results have been corroborated by Gallissian (1963) working
on Eophila dollfusi. If young and adult individuals are amputated and
deprived on cerebral ganglia during periods of functional activity, they
go into diapause and regenerate normally; amputated controls with
intact cerebral ganglia heal but the caudal region is not reconstructed.
The data we have at present for the Oligochaetae are not sufficiently
complete to draw valid conclusions. These experiments must be extended further.
3. Conclusions
From the overall results we have at present, it seems that the brain,
as a source of hormonal substances, is involved in anterior and posterior
regeneration in annelids.
B. Histophysiological Bases
I t is known that hormones issuing from the nervous system are
elaborated in neurosecretory cells essentially characterized, in the
perikaryon, by secretion granules which are eliminated along the
axonal pathway. These cells are present in invertebrates as well as in
vertebrates (Scharrer and Scharrer, 1954; Gabe, 1954; Heller and Clark,
203
exerted by a normal, non-amputated worm; hormonal storage in the
brain seems to have been triggered off simply by transection of the
peripheral nerve fibres at the point of implant.
To conclude, in Polychaetae, it seems that the brain must be present
at the time of posterior transection for regeneration to take place; transection itself triggers off endocrine activity of the cerebral ganglia.
In Oligochaetae, the facts are far from being so well established.
Hubl (1956), experimenting with Eisenia foetida and Allolobophora,
showed that if the supra-oesophageal ganglia were removed at the same
time as posterior amputation was carried out, the capacity for caudal
regeneration was completely inhibited ; on the other hand, if the brain
was removed 1 or 2 days after transection, the posterior segment was
reconstructed normally. He concluded that endocrine function in the
brain was triggered off by transection and that the hormonal discharge
was immediate.
Saussey (1961, 1962) obtained the opposite results with Allolobophora
icteria. He extracted the cerebral ganglia or nervous ganglia up to the
sixth segment in worms during the clitellar phase and simultaneously
cut through the middle of the body; posterior regeneration was much
more rapid in denervated worms than in controls. The rate of reconstruction was directly related to the importance of the part of the nervous system removed. In the species Saussey studied, ganglion extraction
stimulated diapause, a period particularly favourable to regeneration.
Saussey's results have been corroborated by Gallissian (1963) working
on Eophila dollfusi. If young and adult individuals are amputated and
deprived on cerebral ganglia during periods of functional activity, they
go into diapause and regenerate normally; amputated controls with
intact cerebral ganglia heal but the caudal region is not reconstructed.
The data we have at present for the Oligochaetae are not sufficiently
complete to draw valid conclusions. These experiments must be extended further.
3. Conclusions
From the overall results we have at present, it seems that the brain,
as a source of hormonal substances, is involved in anterior and posterior
regeneration in annelids.
B. Histophysiological Bases
I t is known that hormones issuing from the nervous system are
elaborated in neurosecretory cells essentially characterized, in the
perikaryon, by secretion granules which are eliminated along the
axonal pathway. These cells are present in invertebrates as well as in
vertebrates (Scharrer and Scharrer, 1954; Gabe, 1954; Heller and Clark,