364
J. H. 9. BLAXTER AND F. 0. T. HOLLIDAY
His figures do not allow the calculation of the mean duration of each
stage for individual fish. Iles (personal communication) concluded that
there was no simple relationship between the time of maturation and
the time of spawning. The herring could remain for a variable length
of time in a maturity stage, depending on the suitability of the environment for further maturation.
8. Ovulation
The timing of ovulation in the clupeids is closely linked to the time
of spawning, Holliday (1 960b) described ovulation in anaesthetized
herring. A split appeared in the follicle and the egg was extruded
through this (becoming distorted as it did so)-the process taking
about 15 min. The ovulated eggs could be retained for at least 7 days
before spawning, probably maintained at this time by the secretions of
the oviduct. This fluid was apparently taken up by the eggs after
ovulation. Holliday (1 960b) showed that hypophysectomy prevented
ovulation (and sperm release) in the herring. Injection of pituitary
extracts restored these processes.
9. Control of shedding
The elasticity and muscles of the gonad wall, together with the
muscles of the cloaca, exert a close control on the release of the gametes ;
shedding stops if the conditions become unfavourable.
10. Hermaphroditism
This has been described in Sardina pilchardus by dos Santos Pinto
(1953, 1954) and reviewed in the herring by Holliday (1962). It wm
clear that in the herring the male portion8 of the gonad wwcf rnaturhg
at 8 faster rate than the femalc pcmti~ri~ --fiuggwkirIy 14 h i g h r h p !
of responsiveness to the pituitary horrnonf:a by the 8pwrri:~trqrmia BnrJ
spermatocytes than by the oocyfm. However, al~awning ayparcntly
did not take place until both portions of tho gonad wore fully mature.
It is interesting to note that Iles (personal communication) has found
that in the sea the male herring normally mature, stage for stage,
faster than the females and the male herring could be in spawning
condition before the female. Bowers and Holliday (1961) described the
presence of ripe sperm in the testes of male herring as early as Stage 11.
Y. Spawning
1. Spawning grounds
The generJ properties of herring spawning grounds have been
described, for example, by Bolster and Bridger (1057) and by Parrish
J. H. 9. BLAXTER AND F. 0. T. HOLLIDAY
His figures do not allow the calculation of the mean duration of each
stage for individual fish. Iles (personal communication) concluded that
there was no simple relationship between the time of maturation and
the time of spawning. The herring could remain for a variable length
of time in a maturity stage, depending on the suitability of the environment for further maturation.
8. Ovulation
The timing of ovulation in the clupeids is closely linked to the time
of spawning, Holliday (1 960b) described ovulation in anaesthetized
herring. A split appeared in the follicle and the egg was extruded
through this (becoming distorted as it did so)-the process taking
about 15 min. The ovulated eggs could be retained for at least 7 days
before spawning, probably maintained at this time by the secretions of
the oviduct. This fluid was apparently taken up by the eggs after
ovulation. Holliday (1 960b) showed that hypophysectomy prevented
ovulation (and sperm release) in the herring. Injection of pituitary
extracts restored these processes.
9. Control of shedding
The elasticity and muscles of the gonad wall, together with the
muscles of the cloaca, exert a close control on the release of the gametes ;
shedding stops if the conditions become unfavourable.
10. Hermaphroditism
This has been described in Sardina pilchardus by dos Santos Pinto
(1953, 1954) and reviewed in the herring by Holliday (1962). It wm
clear that in the herring the male portion8 of the gonad wwcf rnaturhg
at 8 faster rate than the femalc pcmti~ri~ --fiuggwkirIy 14 h i g h r h p !
of responsiveness to the pituitary horrnonf:a by the 8pwrri:~trqrmia BnrJ
spermatocytes than by the oocyfm. However, al~awning ayparcntly
did not take place until both portions of tho gonad wore fully mature.
It is interesting to note that Iles (personal communication) has found
that in the sea the male herring normally mature, stage for stage,
faster than the females and the male herring could be in spawning
condition before the female. Bowers and Holliday (1961) described the
presence of ripe sperm in the testes of male herring as early as Stage 11.
Y. Spawning
1. Spawning grounds
The generJ properties of herring spawning grounds have been
described, for example, by Bolster and Bridger (1057) and by Parrish