496
SEMEN.
other hand, are cell formations, which de-
velope a seminal fibre in the interior of the
enclosed nucleus.
Of the same filiform shape, and probably
also of the same mode of developement, are the
seminal fibres of the Pychnogonides, which,
according to an observation of Kölliker, mea¬
sure upon an average about -£/" in Pychno-
gonum Balænarum.
Equally filiform and also pointed at both
ends, are the developed spermatozoa of the
Fig. 385.
Developement of the Spermatozoa in Chthamalus
Philippii. (After Kölliker.')
Cirripeds, the size of which, in Chthamalus
Philippii, amounts to about -f/". They are
produced from smaller nucleated cells (of
-i-'"—-i-"'), which would seem, from ex¬
ternal appearances, simply to grow out into
seminal fibres {fig. 385.). An exact research
into the mode of their production is prevented
by the smallness of the cells ; but we need
the less hesitate in inferring the usual en¬
dogenous mode of formation, since we know
how often spermatozoa, on liberating them¬
selves from a mother cell, present, in a most
deceiving manner, the appearance of vesicles
that are growing out.
Little is as yet known respecting the
spermatozoa of the Entomostraca. Here also,
however, the usual filaments occur in the
seminal liquid, in some instances. This may
be proved in the genus Cypris, in which
such formations can readily be traced.*
They are of a considerable length (about 1'"),
and usually wrapped up in the shape of a reel.
Such a form of the spermatozoa does not,
however, seem to be the only one among the
Entomostraca. V.Sieboldf, in Daphnia rec-
tirostris, describes oblong semilunar sper¬
matozoa, whilst Cyclopsina, and probably
also AcanthocereusJ, possess small finely
granular corpuscles of an oval shape, as the
elements of the semen. Similar corpus¬
cles one of us (R. Leuckart with Dr. Frey §,)
* We beg to direct attention to the simultaneous
appearance of eggs together with the spermatozoa
in the same individual ; and therefore to the her¬
maphrodite condition of the genitals in Cypris.
•j- Vergleich : Anat. S. 483.
t According to Schöller, in Wiegman’s Archiv.,
1846, Th. i. S. 367.
§ Ibid. p. 135.
has discovered in Caligus. The production
of these elements, which could be observed in
the latter case, is the same as in lulus. They
at first appear as roundish nuclei in the in¬
terior of the seminal cells, which have a size
of —a ho'"- At this period the nuclei
measure ; they subsequently grow,
change their shape to an oval, and in so doing
not unfrequently project outwards a little be¬
yond the cell wall.
Vesicular seminal elements are also pos¬
sessed by Branchipus*, and oblong cylin¬
drical corpuscles by Staurosoma.f
In their passage through the vas deferens,
the spermatozoa in Cyclopsina, as well as in
the Cephalopoda, &c., are enclosed by one
common jelly-like spermatophore. In some
other cases, on the other hand (as in Onis-
cus), the spermatozoa unite into long flat rib¬
bon-like strings (of 1///), which present quite
an uniform structure, betraying at the ends
only that they are composed of separate semi¬
nal fibres.J
Annelida.—The spermatozoa, in the divi¬
sion of the Annelida, also possess very gene¬
rally a hair-like form, excepting among the
Nematoda. They are thin delicate fibres, ge¬
nerally without any very considerable length
(in Hirudo Planaria varicosa gg", in
Branchiobdella, on the contrary, quite %'"),
which are either pointed towards the ends,
or every where equally thick (in the Tre-
matoda, Acanthocephala, and Cestoidea), or
enlarged at one end.
In Lumbricus {fig. 386. a) the enlarged
part is of an oblong cylindrical form ; in the
Nemertinæ (b) and the branchiated Annelida,
Fig. 386.
Spermatozoa of Lumbricus (a) ; of Nemertis Ehren-
bergii (b) ; and Planaria verrucata (c). (After
Kölliker.)
on the other hand, they are round or pear-
shaped. In some few cases the spermatozoa
among the Annelida exhibit some spiral twin-
ings; as, for instance, in Planaria verru¬
cata (c), Leptoplana atomata, and especially
* Frey and Leuckart in Wagner’s Zootomie, 2d
edit. Part II. p. 259.
f Will in Wiegman’s Archiv., 1844, Th. I.
S. 340.
X Vide Siebold in Miiller’s Archiv. 1836.