Bauhaus-Universität Weimar

Titel:
The Cyclopaedia of Anatomy and Physiology, vol. 4: Pla [corr.: Ple] - Wri
Person:
Todd, Robert Bentley
PURL:
https://digitalesammlungen.uni-weimar.de/viewer/image/lit29465/506/
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.
        

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