296
ELVEZIO GHIRARDELLI
the seminal pouch is placed whose wall is of a syncytial nature.
Between the syncytium and the epithelium a structureless layer is
clearly visible. I n the concavity of the central portion of the crescent
arc the oocytes, and it is possible to observe all the aspects of the
meiotic prophase as well as the several moments of auxocytosis.
BordAs believes that the crescent cells have a trophic function for
the oocytes, and affirms that these cells take the place of those of the
germinal epithelium as they evolve. This idea, however, does not seem
acceptable to me, since forms of transition between nuclei of epithelial
cells and of thc germinal cells are never seen, and furthermore the
cells which constitute the crescent have a different embryonic origin
(Doncaster, 1902; Stevens, 1910). I have not carried out thorough
researches on this material ; I could, however, see that in Spadella one
can discern at very early stages the germinal cells and those of the
supporting elements. According to Stevens (1910) and BordAs (1920)
there exist in the cells of the oviduct wall some contractile differentiations the nature of which has not been ascertained. Vasiljev (1925),
who studied the ovary of Xpadella, believes the supposed differentiation
to be the effect of staining. BordAs (1920) said he also noted a net made
of amorphous elastic lengths, which being attached to the endothelial
cells should constitute the so-called ovarian net whose purpose would
be to support the eggs and protect them until their development was
complete. I have never been able to see in my own preparations anything similar to the ovarian net, and I think that it is probably an
artifact.
I n transverse sections one may observe that the mesentery connecting the ovary to the body wall along the lateral line is formed by
two layers which are a continuation of the thin membrane that wraps
the ovary. When they come in contact with the body walls, the layers
separate and line the coelom cavity ; then they continue and form the
mesenteries that support the intestine. Near the opening of the genital
orifice the mesenteries are no longer visible and the ovary seems to be
directly inserted into the body wall.
Contrary to what BordAs (1914) saw, no communication between the
coelom of the caudal region, where the testes are placed, and the trunk
coelom, where the ovaries are, can be observed either in longitudinal
or transverse sections or in vivo. We must therefore exclude the
possibility that the filling of the seminal pouch may be due to the
direct passage of the spermatozoa from the coelom of the tail to the
ovary.
I n the same species the seminal pouch, when full of spermatozoa
though showing a certain variability, tends to take similar forms. I n
ELVEZIO GHIRARDELLI
the seminal pouch is placed whose wall is of a syncytial nature.
Between the syncytium and the epithelium a structureless layer is
clearly visible. I n the concavity of the central portion of the crescent
arc the oocytes, and it is possible to observe all the aspects of the
meiotic prophase as well as the several moments of auxocytosis.
BordAs believes that the crescent cells have a trophic function for
the oocytes, and affirms that these cells take the place of those of the
germinal epithelium as they evolve. This idea, however, does not seem
acceptable to me, since forms of transition between nuclei of epithelial
cells and of thc germinal cells are never seen, and furthermore the
cells which constitute the crescent have a different embryonic origin
(Doncaster, 1902; Stevens, 1910). I have not carried out thorough
researches on this material ; I could, however, see that in Spadella one
can discern at very early stages the germinal cells and those of the
supporting elements. According to Stevens (1910) and BordAs (1920)
there exist in the cells of the oviduct wall some contractile differentiations the nature of which has not been ascertained. Vasiljev (1925),
who studied the ovary of Xpadella, believes the supposed differentiation
to be the effect of staining. BordAs (1920) said he also noted a net made
of amorphous elastic lengths, which being attached to the endothelial
cells should constitute the so-called ovarian net whose purpose would
be to support the eggs and protect them until their development was
complete. I have never been able to see in my own preparations anything similar to the ovarian net, and I think that it is probably an
artifact.
I n transverse sections one may observe that the mesentery connecting the ovary to the body wall along the lateral line is formed by
two layers which are a continuation of the thin membrane that wraps
the ovary. When they come in contact with the body walls, the layers
separate and line the coelom cavity ; then they continue and form the
mesenteries that support the intestine. Near the opening of the genital
orifice the mesenteries are no longer visible and the ovary seems to be
directly inserted into the body wall.
Contrary to what BordAs (1914) saw, no communication between the
coelom of the caudal region, where the testes are placed, and the trunk
coelom, where the ovaries are, can be observed either in longitudinal
or transverse sections or in vivo. We must therefore exclude the
possibility that the filling of the seminal pouch may be due to the
direct passage of the spermatozoa from the coelom of the tail to the
ovary.
I n the same species the seminal pouch, when full of spermatozoa
though showing a certain variability, tends to take similar forms. I n