$ 129. THE TURBELLARIA. 1389 
The following are the parté usually found: an ovary or organ of vitel- 
line secretion, which is double, and, extending into the parenchyma of the 
body, opens by a common excretory duct into a large cavity, —a vagina or 
oviduct; a double testicle sends its seminal liquid, full of filamentoid and 
motionless spermatic particles, into the seminal vesicle through two tor- 
tuous vasa deferentia; to this seminal vesicle is attached a very erectile 
penis, situated by the side of the vagina. There is a common genital open- 
ing, situated always behind the mouth, for the protrusion of this penis and 
the escape of the eggs. 
With Planaria, there are, beside, two special, hollow organs, with narrow 
excretory ducts, which open into the vagina. 
Of these, one very probably 
secretes the envelope of the egg, while the other serves as a Receptaculum 
seminis.® 
§ 129. 
The embryonic development of the Turbellaria is yet unknown except 
with the Planariae. 
It differs wholly from anything yet known with other Invertebrates. 
Many of these embryos are developed, always simultaneously, in one 
large egg; but it is impossible at first to determine their number, since 
4 See, for the genital organs of Mesostomum Eh- 
renbergui, Focke (loc. cit.); for those of Plano- 
cera,and Leptoplana, Mertens (loc. cit.); and for 
those of Derostomum, and Planaria, Duges, 
Baer, and Orsted (loc. cit.). But the interpretation 
here given of the different parts of these organs 
must be much changed. For, to speak here only 
of the genus Planaria, what Baer has regarded 
as the ovaries and oviducts,: are certainly the two 
testicles with their vasa deferentia, since I have 
always found them filled with spermatic particles 
(loc. cit. Tab. XXIII. fig. 18, a. b.). The two sem- 
inal canals open into a hollow, flask-shaped body 
like a Vesicula seminalis or a Ductus ejacu- 
tatorius, the neck of which is continuous with a 
very contractile and erectile tube (Penis). This 
penis is in a cavity separated by a septum from 
the large vulva, with which, however, it communi- 
cates by a special orifice, and consequently can be 
protracted through the common genital opening. 
There is, beside the intestinal canal, another rami- 
fied organ in the body of Planaria, and whieh 
very probably is an ovary, or at least a vitellus- 
secreting organ. But its caeca contain only simple 
vesicular bodies, which have no germinative vesi- 
cles. The canal which Duges (loc. cit. XV. Pl. V. 
fig. 4, b.) has taken for an oviduct, belongs prob- 
ably to the ramifications of this organ. The other 
two organs which this author (Ibid. Pl. V. fig. 4, 
8, c.) has described as Vésicule copulatrice ou 
réservoir du sperme et des oeufs, do not appear 
to me to exist in all Planariae. They consist of two 
hollow, pyriform organs, not blended together as 
Duges has figured them, but distinct ; one opens 
by a long, and the other by a shorter canal, into 
* [ § 128, note 4.) See, for many details on the 
sexual organs of the Turbellaria, and illustrated 
the vulva. As I have found many spermatic par- 
ticles in the first of these, I am led to regard it as 
a Receptaculum seminis. But in the other, 
which Baer (loc. cit. Tab. XX XIII. fig. 18, e.) has 
taken for a penis, I have never found either eggs 
or germs, but always only a granular substance ; 
from this I am inclined to think that this organ se- 
cretes the material which envelops the vitelline 
cells grouped in the vulva. With the Planariae, 
one egg at a time is always formed in the round 
vagina ; this is very large, and when it is de- 
posited others succeed it inthe same way. This is 
not true, however, with Mesostomum Ehren- 
bergii ; here the vagina is short and narrow, 
and receives various organs whose nature is 
not yet well determined. One of these contains, 
according to my own researches, a confused mass 
of active, filamentoid spermatic particles, and may 
therefore be regarded as a Receptaculum sem- 
inis. Two canals which pass off right and left 
from the vagina, bifurcate into two simple coeca, 
one of which passes forwards, and the other back- 
wards, and in which very large eggs remain for a 
long time. This therefore may be regarded as an 
uterus. See Focke, Taf. XVII. fig. 1, 11, g. g. 
According to the very minute researches of 
Quatrefages (loc. cit. p. 163, Pl. TV.-VII.) made 
upon various marine Planarzae, both the male and 
the female organs of these Dendrccoéli have two 
distinct orifices situated in the ventral region, one 
behind the other. The posterior is a vulva and 
opens into amore or less long coecum (vagina or 
copulatory pouch) upon which are laterally inserted 
two oviducts. The anterior orifice is for the pro- 
trusion of the protractile penis.* 
spermatic particles of the Planariae is littleunder- 
stood. They probably have not a hair-like form as 
with figures, Schmidt, loc. cit. (Prot 
Vortex, Hypost » Dero. » Meso- 
t , Op » Macrost , Microsto- 
mum, St » Schi: » Typhlo- 
plana ; according to this author, Dinophilus vor- 
ticotdes is separate-sexed,—the exceptional in- 
stance among the Rhabdocoeli. The subject of the 
tioned in the preceding note, but are Cercaria~ 
like ; see Kélltker, loc. cit., Quatrefages, loc. cit. 
Pl. VII. fig. 5-9, and Schmidt, Die Rhabdoc. 
Strudelwiirmer, &c., p. 16; this author, however, 
describes those of Opistomum pallidum as some- 
what different, there being a filament beyond the 
head (Taf. V. fig. 14>). — Ep. 
. 
