SOME ASPECTS O F THE BIOLOGY O F T H E CHAETOGNATHS
185
charides are present but not glycogen ; the common origin of the corona
and ventral ganglion makes it not so surprising that the glandular part
of the ciliary loop elaborates a product that presents some characteristics
of a neurosecretion.
Great caution is, however, advisable in extending to chaetognaths
conclusions deriving from researches carried out with methods used on
animals often quite far removed on the zoological scale (Ghirardelli,
195813). Gabe (1966) also states that the cells of the inner corona are
of ectodermal origin, but they do not possess any of the morphological
characters of neurons. They could still be considered as glandular and
not neuroglandular. The staining affinities cannot be regarded as
proving the neurosecretory nature of the product of the ( ( corona
ciliata ”.
The finely granular secretion of the corona spreads and distributes
itself on the cuticle or is interposed with the thinnest cuticular plates
on the surface of the body, generally along the median dorsal line. Tt,
finally gathers quite abundantly near the female genital orifices and
directly inside them. The regions that are richer in grains, i.e. the
corona and the region of the genital orifices up to the seminal receptscles, when observed through the fluorescence microscope, show the
same yellow-green fluorescence which is peculiar to flavins. The
distribution and diffusion of the grains coincides remarkably, as we
shall see later, with the course followed by the spermatozoa after
copulation. The coincidence of the two paths may then lead t o the idea
that in Xpadella the grains of secretion may perhaps have some function
in regulating the migration of the spermatozoa (see p. 324). My
observations practically confirm Reisinger’s description as regards the
outer and inner rings. Some doubts, however, remain about the real
existence of the annular canal as a persistent formation. Actually the
features seen by Reisinger and by myself could be due t o a series of
vacuoli more or less empty or full according to the physiological
condition of the individual, rather than to the presence of a continuous
and persisting canal.
Still less proved is the excretory function of the ciliated crown : it
has no relation to the coelom, since it is an organ completely situated
on the epidermis in the region of the neck, partially in that peculiar
differentiation of the epidermis called the collarette (lateral areas of
the epidermis according to Grassi) which has no relation even with the
underlying musculature. The ring is so superficial that it can easily
be isolated from the body by mechanical means, especially in Spaddla.
Moreover, in Sagitla it is rather difficult for it to be preserved in its
entirety in specimens captured by plankton nets. The least friction is
185
charides are present but not glycogen ; the common origin of the corona
and ventral ganglion makes it not so surprising that the glandular part
of the ciliary loop elaborates a product that presents some characteristics
of a neurosecretion.
Great caution is, however, advisable in extending to chaetognaths
conclusions deriving from researches carried out with methods used on
animals often quite far removed on the zoological scale (Ghirardelli,
195813). Gabe (1966) also states that the cells of the inner corona are
of ectodermal origin, but they do not possess any of the morphological
characters of neurons. They could still be considered as glandular and
not neuroglandular. The staining affinities cannot be regarded as
proving the neurosecretory nature of the product of the ( ( corona
ciliata ”.
The finely granular secretion of the corona spreads and distributes
itself on the cuticle or is interposed with the thinnest cuticular plates
on the surface of the body, generally along the median dorsal line. Tt,
finally gathers quite abundantly near the female genital orifices and
directly inside them. The regions that are richer in grains, i.e. the
corona and the region of the genital orifices up to the seminal receptscles, when observed through the fluorescence microscope, show the
same yellow-green fluorescence which is peculiar to flavins. The
distribution and diffusion of the grains coincides remarkably, as we
shall see later, with the course followed by the spermatozoa after
copulation. The coincidence of the two paths may then lead t o the idea
that in Xpadella the grains of secretion may perhaps have some function
in regulating the migration of the spermatozoa (see p. 324). My
observations practically confirm Reisinger’s description as regards the
outer and inner rings. Some doubts, however, remain about the real
existence of the annular canal as a persistent formation. Actually the
features seen by Reisinger and by myself could be due t o a series of
vacuoli more or less empty or full according to the physiological
condition of the individual, rather than to the presence of a continuous
and persisting canal.
Still less proved is the excretory function of the ciliated crown : it
has no relation to the coelom, since it is an organ completely situated
on the epidermis in the region of the neck, partially in that peculiar
differentiation of the epidermis called the collarette (lateral areas of
the epidermis according to Grassi) which has no relation even with the
underlying musculature. The ring is so superficial that it can easily
be isolated from the body by mechanical means, especially in Spaddla.
Moreover, in Sagitla it is rather difficult for it to be preserved in its
entirety in specimens captured by plankton nets. The least friction is