gamctes. ‘ I ’ h t w facts must
tdwn iiito consideration when interpreting thch rwults of‘ expcxirncnts on t h hormonal co~it~rol of reproduction.
Although Huus (1937) did not postulate the presence of a gonadotrophin, and in fact considered the neural gland as the homologue of
the posterior pituitary only, he suggested that the gland controlled the
reproductive process. He considered that the ciliated funnel would
collect stim dating substances (i.e. gametes from neighbouring a~cidians
of the same species) and thesc would stimulate a secretion from the
neural gland which, transported in the blood stream to the gonads,
would stimulate discharge of gametes. In the same year Hogg (1937)
using Polycnrpa obtecta Traustedt carried out the first experiments
aimed at identifying a gonad stimulating activity in the neural complex,
by injecting extracts into three mice while three controls received
injections of saline. Five days later autopsy revealed that on average
the gonads of the experimental animals were three times as heavy as
those of the controls kind the follicles in the former were larger and more
numerous than in the latter. Carlisle (1950c), using Ciona intestinal&
and Phallusin ni,arnmillnta, obtained similar results using three test
mice and two controls into which he injected extracts of tissues other
than from neural gland. He also reported that extracts of neural
gland injected into male frogs caused discharge of sperm. These results
are in conflict with those of Benazzi (1939) and Dodd (1955). Benazzi
obtained negative results when extracts of neural gland were injected
into five mice ;md he W i t s unable to produce ovulation in newts when
injected with extracts of neural complex. Dodd obtained only one
positive result from ten mice injected with extracts from neural complexes of Ciona inieatinalis, and no positive results following similar
injections into male Xenopus laevis. Dodd suggested that seasonal
variation might accouiit for these discordant results but a t the same
time points out that his material came from ascidians which were
sexually ripe and that therefore if gonadotrophin exists at all it should
have been revealed in his own experiments.
All of the above experiments were based on the premise that if a
gonadiul hormone is present in the ascidian neural complex it will have
properties similar to those found in vertebrates. But this may not be a
reasonable premise and experimentalists may be on much safer ground
if they use ascidian material upon which to tegt their extracts, at leaRt
in the first instance.
In an interesting but con troversial series of experiments Carlisle
(1961) attempted to show that the neural gland and nerve ganglion
were intimately associated in the neuro-humoral control of gclmcterelease and the ~ynrhronization of spawning. Following the lead already
tdwn iiito consideration when interpreting thch rwults of‘ expcxirncnts on t h hormonal co~it~rol of reproduction.
Although Huus (1937) did not postulate the presence of a gonadotrophin, and in fact considered the neural gland as the homologue of
the posterior pituitary only, he suggested that the gland controlled the
reproductive process. He considered that the ciliated funnel would
collect stim dating substances (i.e. gametes from neighbouring a~cidians
of the same species) and thesc would stimulate a secretion from the
neural gland which, transported in the blood stream to the gonads,
would stimulate discharge of gametes. In the same year Hogg (1937)
using Polycnrpa obtecta Traustedt carried out the first experiments
aimed at identifying a gonad stimulating activity in the neural complex,
by injecting extracts into three mice while three controls received
injections of saline. Five days later autopsy revealed that on average
the gonads of the experimental animals were three times as heavy as
those of the controls kind the follicles in the former were larger and more
numerous than in the latter. Carlisle (1950c), using Ciona intestinal&
and Phallusin ni,arnmillnta, obtained similar results using three test
mice and two controls into which he injected extracts of tissues other
than from neural gland. He also reported that extracts of neural
gland injected into male frogs caused discharge of sperm. These results
are in conflict with those of Benazzi (1939) and Dodd (1955). Benazzi
obtained negative results when extracts of neural gland were injected
into five mice ;md he W i t s unable to produce ovulation in newts when
injected with extracts of neural complex. Dodd obtained only one
positive result from ten mice injected with extracts from neural complexes of Ciona inieatinalis, and no positive results following similar
injections into male Xenopus laevis. Dodd suggested that seasonal
variation might accouiit for these discordant results but a t the same
time points out that his material came from ascidians which were
sexually ripe and that therefore if gonadotrophin exists at all it should
have been revealed in his own experiments.
All of the above experiments were based on the premise that if a
gonadiul hormone is present in the ascidian neural complex it will have
properties similar to those found in vertebrates. But this may not be a
reasonable premise and experimentalists may be on much safer ground
if they use ascidian material upon which to tegt their extracts, at leaRt
in the first instance.
In an interesting but con troversial series of experiments Carlisle
(1961) attempted to show that the neural gland and nerve ganglion
were intimately associated in the neuro-humoral control of gclmcterelease and the ~ynrhronization of spawning. Following the lead already