292
ELVEZIO GHTRARDELLI
B. The female reproductive apparatus. General
The first detailed description of the morphology of the female
reproductive apparatus in chaetognaths was given by Grassi in 1883.
Earlier observations by Butschli (1873, Hertwig (1880) and Crassi
himself (1881) are only short notes. Hertwig, by the way, argued
mistakenly that the germinal epithelium had a syncytial nature and
that the so-called oospermaduct is situated outside the ovary.
According to the description by Grassi (1883), which pre-eminently
refers to the genera Xagitta and Xpadella, the female reproductive
organs in Chaetognatha are formed by two cylindrical ovaries placed
in the trunk coelom before the caudal septum, one at the right and one
a t the left of the intestine. I n young specimens they occupy a small
part of the lateral posterior coelom of the trunk.
The germinal epithelium of the ovary, still according to Grassi,
appears in transverse sectioiis as a “ lobed crown ” in which four parts
can be distinguished : one outer part corresponding to the attachment
line on the body wall, one inner towards the intestine, one dorsal and
lastly a ventral part. These parts can be distinguished by the different
forms of their cellular elements.
Oocytes still far from maturity have a kind of peduncle which,
according to Grassi, consists of an inflated cell. The ovary is enclosed
in an involucre consisting of a layer of polygonal cells, reinforced on
the inner surface by a thin layer of fibrils from which transverse
sepiments arise directed towards the inside. From the anterior end of
the ovary a fibrous ligament arises, ending at the level of the ventral
ganglion ; another short fibrous ligament connects the posterior end of
the ovary t o the transverse septum near to the anus.
On each ovary, in proximity to the line of attachment to the body
wall, runs the “ oospermaduct ”, a thin canal so called by Grassi
because (‘ it carries the sperm to the eggs and the eggs to the outside,
but it also has functions of a spermatheca ”. As regards this structure,
there are the greatest differences of opinion among several authors.
Krohn (1853), Leuckart and Pagenstecher (1858) had described it
as a sperm pouch (Xamentasche). Keferstein (1862) believed it to be an
oviduct, Wilms (1844) an excretory duct, and Huxley (1852) considered
it to be a ciliated canal. Still according to Grassi, the lumen of the
sperm-oviduct varies in relation to the quantity of spermatozoa
contained in it, and its wall is composed of a single layer of cells.
Stevens (1910) and Elpatiewsky (1913), on the other hand, describe
two layers of cells of which the inner one is a syncytium. Stevens has
described the ‘( lobed crown ” of Grassi as formed by two layers of
ELVEZIO GHTRARDELLI
B. The female reproductive apparatus. General
The first detailed description of the morphology of the female
reproductive apparatus in chaetognaths was given by Grassi in 1883.
Earlier observations by Butschli (1873, Hertwig (1880) and Crassi
himself (1881) are only short notes. Hertwig, by the way, argued
mistakenly that the germinal epithelium had a syncytial nature and
that the so-called oospermaduct is situated outside the ovary.
According to the description by Grassi (1883), which pre-eminently
refers to the genera Xagitta and Xpadella, the female reproductive
organs in Chaetognatha are formed by two cylindrical ovaries placed
in the trunk coelom before the caudal septum, one at the right and one
a t the left of the intestine. I n young specimens they occupy a small
part of the lateral posterior coelom of the trunk.
The germinal epithelium of the ovary, still according to Grassi,
appears in transverse sectioiis as a “ lobed crown ” in which four parts
can be distinguished : one outer part corresponding to the attachment
line on the body wall, one inner towards the intestine, one dorsal and
lastly a ventral part. These parts can be distinguished by the different
forms of their cellular elements.
Oocytes still far from maturity have a kind of peduncle which,
according to Grassi, consists of an inflated cell. The ovary is enclosed
in an involucre consisting of a layer of polygonal cells, reinforced on
the inner surface by a thin layer of fibrils from which transverse
sepiments arise directed towards the inside. From the anterior end of
the ovary a fibrous ligament arises, ending at the level of the ventral
ganglion ; another short fibrous ligament connects the posterior end of
the ovary t o the transverse septum near to the anus.
On each ovary, in proximity to the line of attachment to the body
wall, runs the “ oospermaduct ”, a thin canal so called by Grassi
because (‘ it carries the sperm to the eggs and the eggs to the outside,
but it also has functions of a spermatheca ”. As regards this structure,
there are the greatest differences of opinion among several authors.
Krohn (1853), Leuckart and Pagenstecher (1858) had described it
as a sperm pouch (Xamentasche). Keferstein (1862) believed it to be an
oviduct, Wilms (1844) an excretory duct, and Huxley (1852) considered
it to be a ciliated canal. Still according to Grassi, the lumen of the
sperm-oviduct varies in relation to the quantity of spermatozoa
contained in it, and its wall is composed of a single layer of cells.
Stevens (1910) and Elpatiewsky (1913), on the other hand, describe
two layers of cells of which the inner one is a syncytium. Stevens has
described the ‘( lobed crown ” of Grassi as formed by two layers of