$115. THE HELMINTHES. 121 
_ The neck of the internal seminal vesicle (Vesicula seminalis interior), 
‘lischarges its contents at thissame place into the uterus, through a special 
Vas deferens from one of the testicles. The Uterus commences as a narrow 
tube, which may be regarded as a Tuba Fallopii. Its dilated portion, 
‘which has powerful peristaltic motions notwithstanding its thin walls, is 
throughout of nearly an equal diameter. It winds through a large portion 
of the body and terminates in a narrow, more or less straight, muscular 
vagina, which always opens externally by the side of the penis. 
The testicles, of which there are usually two,® are generally of a round 
or oval form, and located in the posterior region of the body, nearly 
always one before the other. They are transparent and colorless, and 
the filiform spermatic particles are extremely small and active.® The 
two Vasa deferentia open into the cirrhus-sac, which is perforated at its 
\bottom to communicate with the Vesicula seminalis exterior. From 
each testicle there passes off, also, a third Vas deferens which opéns into 
the neck of the Vesicula seminalis interior. The cirrhus-sac is pyri- 
formly elongate, or round, and the Vesicula seminalis exterior is always 
situated at its base. This last is prolonged, opposite the openings of the 
‘vasa deferentia, into usually a very long, tortuous Ductus ejaculatorius, 
which opens into a tubular penis.“ There is on¢ common genital open- 
ing for the penis and vagina which are usually side by side, and out of 
which the penis often considerably projects.” In most Trematodes, these 
two organs are located at the anterior extremity of the body, and only in 
_Holostomum, and Gasterostomum, are they removed to the other extrem- 
é ity. 18) 
8 The length of the uterus varies very much in 
different genera and species, and its coils are 
always irregular. - With Monostomum mutabile, 
and verrucosum, the oviduct arising in the poste- 
“rior extremity, passes in front with numerous 
transverse coils. 
don nhiet, 
perceived unless they are quite isolated. When 
put in water they become twisted together, and 
assume a loop-like arr  — their i 
instantly ceasing. 
For the development of the spermatic particles 
of the Trematodes, see Kélliker, Die Bildung du 
98 Ihave found one testicle only, in 
mum subclavatum, and Aspidogaster conchicola, 
although I have seen three or four in Distomum 
appendiculatum, and cygnoides. 
With Di. tum, the two are 
side by side behind the ventral sucker ; with Dis- 
tomum chilostomum, they are on each side of this 
sucker, and with Distomum crassum, mihi (from 
‘the intestine of Hirundo domestica), they are in 
front of it, on each side of the neck. 
ll With Distomum longicolle, lanceolatum, 
woxyurum, echinatum, globiporum, and Amphis- 
icum, icles have many depres- 
‘sions 3 see Bojanus, Isis, 1821, Taf. IL. fig. 25-27 ; 
Burmeister and Siebold, in Wiegmann's Arch. 
1835, IL. Taf. II. 1836, I. Taf. VI. ; also Laurer, 
De Amphistomo conico. fig. 21, 24, 25. With 
Amphistomum subtriquetrum, giganteum, and 
Distomum hians, the number and depth of these 
depressions gives the testicle the aspect of a bundle 
of caeca; see Bojanus, loc. cit. Taf. II. fig. 14-17, 
and Diesing Ann. d. Wiener Mus. I. Abth. 2, 
Taf. XXII. 
12 In the of the Tr , the devel- 
opment of the spermatic particles occurs after the 
usual mode. 
The bundles which they form are separated in 
their passing the vasa deferentia, and they collect 
into irregular masses in the seminal vesicles. 
Their extremely active movements cannot be 
tod 
*[§ 115, note 12.] Thaer (Muller's Arch. 1850, 
Pp. 602, Taf. XXI. fig. 19) has described and fig- 
11 
8 faden in Blaschen, loc. cit. p. 44, fig. 31.* 
18 These two vasa deferentia are sometimes 
blended together before reaching their destina- 
tion; this is soin Distomum variegatum, and 
longicolle. 
14 The internal seminal vesicle is so extraordi- 
narily large in Distomum variegatum that it 
exceeds that of the ovary and two testicles. 
15 This cirrhus-sac, together with the penis, is 
very long with Di. lima, le ; 
variegatum, and ovatum ; but it is especially so 
with Aspidogast hicola, and M 
verrucosum. 
16 The protruding cirrhus or penis of Distomum 
holostomum is provided with small bunches ; and 
that of Monostomum verrucosum with num- 
berless little warts. 
17 When the penis is protruded, it may then be 
seen how the contents of the vagina are emptied at 
its base. When the common genital opening is 
closed, the very flexible penis can be turned into the 
vagina and there discharge its contents, and in 
this way the self-impregnation of these animals 
may occur. 
18 The common genital opening is usually sit- 
uated on the middle of the neck, and with Dis- 
tomum, it is directly infront of the ventral sucker. 
With Distomum clavigerum, and ovatum, it is 
upon the sides of the neck, and with Distomum 
dale, and hol e bly, it is on 
:] 
ured the spermatic particles of Polystomum ap- 
pendiculatum as Cercaria-form. — Ep. 
