332
ELVEZIO GHIRARDELLI
conditions may have already been fertilized before, by spermatozoa
originating from another individual. I n cases of self-fertilization he has
been able to fully confirm Jagersten’s findings that the spermatozoa
migrate along the caudal segment towards the seminal receptacles
which are quickly filled. Nevertheless Dallot does not exclude, as
Jagersten did, the possibility of a mating in S. setosu: but if it does
exist, it is not essential for the survival of the species.
At this point an histological control of the state of filling of the
seminal receptacles would be desirable, since sperms present in receptacles which are not completely full escape direct observation through
the binocular ; subordinately it should be quite interesting to raise in
isolation some specimens from the egg up to the stage of full sexual
maturity: only in this way could absolute certainty be reached that
the sperms present in the seminal receptacles derive from the seminal
vesicles of the same specimen.
Dallot’s supposition that self-fertilization does not exclude crossed
fertilization, remains valid : we would add that crossed fertilization does
not exclude the possibility of self-fertilization. Even Jagersten’s theory
that cross-fertilization was gradually replaced in the course of phylogeny
by self-fertilization may be suggestive, but the presence of peculiar
formations on the seminal vesicles is far too constant t o be void of any
functional value in the present. The seminal vesicles in AS’ . inJEatu are
indeed always surmounted by a small cup with smooth edges, while in
S. bipunctuta the edges are shaped like saw teeth ; the different forms of
S. serratodentatu are recognizable by the different aspects of their
seminal vesicles. Nearby these structures there is generally a point
where the seminal vesicles are thinner, and this is, therefore, considered
to be the orifice of the vesicles (Tokioka, 1939a, 1942; Kuhl, 1938;
Jagersten, 1940 ; Ghirardelli, 1950a, 1954a, 1959c, 1962 ; Furnestin,
1957).
I have also been able t o confirm the observations made by Jagersten
on 8. setosa, trying more than once and without result t o induce mating
in AS’ . inJEata and S. bipunctatu. On the contrary, the mature spermatophores of these two species can be detached quite easily, together with
the small cup that closes the orifice of the seminal vesicles, and made
to adhere with the same cup t o the body of a specimen of the same
species. If the spermatophores are placed on the back, they do not
adhere well and one does not observe any migration of spermatozoa as
in Spudella. Sometimes the spermatozoa form regular streams and very
occasionally they head towards the openings of the seminal receptacles ;
but when the spermatophore is put on the genital papilla or in its
immediate neighbourhood, one can see the rapid penetration of the
ELVEZIO GHIRARDELLI
conditions may have already been fertilized before, by spermatozoa
originating from another individual. I n cases of self-fertilization he has
been able to fully confirm Jagersten’s findings that the spermatozoa
migrate along the caudal segment towards the seminal receptacles
which are quickly filled. Nevertheless Dallot does not exclude, as
Jagersten did, the possibility of a mating in S. setosu: but if it does
exist, it is not essential for the survival of the species.
At this point an histological control of the state of filling of the
seminal receptacles would be desirable, since sperms present in receptacles which are not completely full escape direct observation through
the binocular ; subordinately it should be quite interesting to raise in
isolation some specimens from the egg up to the stage of full sexual
maturity: only in this way could absolute certainty be reached that
the sperms present in the seminal receptacles derive from the seminal
vesicles of the same specimen.
Dallot’s supposition that self-fertilization does not exclude crossed
fertilization, remains valid : we would add that crossed fertilization does
not exclude the possibility of self-fertilization. Even Jagersten’s theory
that cross-fertilization was gradually replaced in the course of phylogeny
by self-fertilization may be suggestive, but the presence of peculiar
formations on the seminal vesicles is far too constant t o be void of any
functional value in the present. The seminal vesicles in AS’ . inJEatu are
indeed always surmounted by a small cup with smooth edges, while in
S. bipunctuta the edges are shaped like saw teeth ; the different forms of
S. serratodentatu are recognizable by the different aspects of their
seminal vesicles. Nearby these structures there is generally a point
where the seminal vesicles are thinner, and this is, therefore, considered
to be the orifice of the vesicles (Tokioka, 1939a, 1942; Kuhl, 1938;
Jagersten, 1940 ; Ghirardelli, 1950a, 1954a, 1959c, 1962 ; Furnestin,
1957).
I have also been able t o confirm the observations made by Jagersten
on 8. setosa, trying more than once and without result t o induce mating
in AS’ . inJEata and S. bipunctatu. On the contrary, the mature spermatophores of these two species can be detached quite easily, together with
the small cup that closes the orifice of the seminal vesicles, and made
to adhere with the same cup t o the body of a specimen of the same
species. If the spermatophores are placed on the back, they do not
adhere well and one does not observe any migration of spermatozoa as
in Spudella. Sometimes the spermatozoa form regular streams and very
occasionally they head towards the openings of the seminal receptacles ;
but when the spermatophore is put on the genital papilla or in its
immediate neighbourhood, one can see the rapid penetration of the