SOME ASPECTS O F THE BIOLOGY O F THE CHAETOGNATHS
347
are massed without any definite order. S. inJlata with long ovaries has
the tail section proportionately shorter than the form with short
ovaries. It was thought at first (Ghirardelli, 1951, 1952) that they were
two separate races or two ecotypes. Later it appeared more probable
that the two forms of S. inJlata are but two aspects connected with
sexual maturity. Such conclusions are confirmed by cytological
researches on the stages of sexual maturity (Ghirardelli, 1961a).
Through these researches it has also been possible to confirm the
protandry of S. inJlata and the existence of at least two successive
cycles of activity by the female gonads. The short-ovaried form almost
certainly corresponds to the first period of maturity of the ovaries, the
long-ovaried form to a later period of sexual maturity. Both in the
first and in the second form, there may be at least two separate phases
of sexual maturity of the ovary.
Furnestin (1957) has come to the same conclusion as far as the
Mediterranean specimens are concerned ; in the tropical Atlantic she
has observed that there can be three or even four phases of maturity.
Also S. inJlata of Spanish waters shows, according to Massuti-Oliver
(1954) two phases of sexual maturity, one in February-March and one
in October. By biometrical research (Ghirardelli, 1962) further confirmation has been obtained of the data provided by the cytologica1
researches and thc direct observation of living specimens. Indeed, the
length of the gonads, though not always strictly related to the total
lcngth, is nevertheless connected with the dimensions of the specimens
and actually with their age. It is, however, apparent that, the total
lengths being the same, there may be specimens whose ovaries show
quite different dimensions (in connexion with the stage of maturity)
since there may be individuals more or less mature in their female sex,
or there may also be individuals which have just laid their eggs, and in
these the ovary, as we have said, undergoes a remarkable shortening.
Similar observations have been made on X. setosa by Dallot (1966,
1967). Cytologically, such secondarily shortened ovaries show the
same features as those of specimens which have for the first time
reached a younger maturity stage, namely stage 2, corresponding to
the second growth period of the oocytes (Ghirardelli, 1961a,c). If one
considers that at a length of 11 mm in the Gulf of Naples there are
already mature specimens (for Furnestin, 1957, the minimum length
should be 13 mm), and that there are mature specimens also at 18 mm,
the reasons for the great variability of the ovaries in comparison with
the total length of the animal become still clearer.
The existence of two groups of individuals is also confirmed
by the diagrams showing the ratios of the total length and
347
are massed without any definite order. S. inJlata with long ovaries has
the tail section proportionately shorter than the form with short
ovaries. It was thought at first (Ghirardelli, 1951, 1952) that they were
two separate races or two ecotypes. Later it appeared more probable
that the two forms of S. inJlata are but two aspects connected with
sexual maturity. Such conclusions are confirmed by cytological
researches on the stages of sexual maturity (Ghirardelli, 1961a).
Through these researches it has also been possible to confirm the
protandry of S. inJlata and the existence of at least two successive
cycles of activity by the female gonads. The short-ovaried form almost
certainly corresponds to the first period of maturity of the ovaries, the
long-ovaried form to a later period of sexual maturity. Both in the
first and in the second form, there may be at least two separate phases
of sexual maturity of the ovary.
Furnestin (1957) has come to the same conclusion as far as the
Mediterranean specimens are concerned ; in the tropical Atlantic she
has observed that there can be three or even four phases of maturity.
Also S. inJlata of Spanish waters shows, according to Massuti-Oliver
(1954) two phases of sexual maturity, one in February-March and one
in October. By biometrical research (Ghirardelli, 1962) further confirmation has been obtained of the data provided by the cytologica1
researches and thc direct observation of living specimens. Indeed, the
length of the gonads, though not always strictly related to the total
lcngth, is nevertheless connected with the dimensions of the specimens
and actually with their age. It is, however, apparent that, the total
lengths being the same, there may be specimens whose ovaries show
quite different dimensions (in connexion with the stage of maturity)
since there may be individuals more or less mature in their female sex,
or there may also be individuals which have just laid their eggs, and in
these the ovary, as we have said, undergoes a remarkable shortening.
Similar observations have been made on X. setosa by Dallot (1966,
1967). Cytologically, such secondarily shortened ovaries show the
same features as those of specimens which have for the first time
reached a younger maturity stage, namely stage 2, corresponding to
the second growth period of the oocytes (Ghirardelli, 1961a,c). If one
considers that at a length of 11 mm in the Gulf of Naples there are
already mature specimens (for Furnestin, 1957, the minimum length
should be 13 mm), and that there are mature specimens also at 18 mm,
the reasons for the great variability of the ovaries in comparison with
the total length of the animal become still clearer.
The existence of two groups of individuals is also confirmed
by the diagrams showing the ratios of the total length and