§115. 



THE HELMINTHES. 



121 



The neck of the internal seminal vesicle [Vesicula seminalis interior), 

 discharges its contents at this same 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 portionj 

 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 opens into 

 the neck of the Vesicula seminalis hiterior.^^^'* The cirrhus-sac is pyri- 

 formly elongate, or round, ''^' and the Vesicula soninalis 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 one 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- 

 ity. 'i«> 



8 The length of the uterus varies very much in 

 different genera and species, and its coils are 

 always irregular. With Monoslomum mutabilc, 

 and verrucosum, the oviduct arising in the poste- 

 rior extremity, passes in front with numerous 

 transverse coiJs. 



y I have found one testicle only, in Amphisto- 

 mum subclavatum, and Aspidogaster conchicola, 

 although I have seen three or four in Distomum 

 appendiculatum, and cygnoides. 



10 With Distomum ovatum, the two testicles are 

 side by side behind the ventral sucker ; with Dis- 

 tomum cliitostomum, they are on each side of this 

 sucker, and with Distomum crassum^ mihi (from 

 the intestine of Hirundo dume.itica), they are in 

 front of it, on each side of the neck. 



11 With Distomum longicoUe, lanceolatum, 

 oxyuTum,, echinatnm, glohiporum, and Amphis- 

 tomum conicum, the testicles have many depres- 

 sions ; see Bojanus, Isi3,182], Taf. II. fig. 25-27 ; 

 Burmeister and Sieliold, in fViegm.ann's Arch. 

 1835, II. Taf. II. 1836, I. Taf. VI. ; also Laurer, 

 De Ampliistomo conioo. fig. 21, 24, 25. With 

 Amphistomum .tuOtrir/uetrum, giganteum, and 

 Distomum liians, tlic 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 testicles of the Trematodes, 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 



perceived vuiless they are quite isolated. When 

 put in water they become twisted together, and 

 assume a loop-like arrangement, — their motions 

 instantly ceasing. 



For the development of the spermatic particles 

 of the Trematodes, see KbUiker, Die Bildung du 

 Saamenfiiden in Blaschen, loc. cit. p. 44, fig. 31.* 



lo These two vasa deferentia are sometimes 

 blended together before reaching their destina- 

 tion ; this is so in Distomum. variegatum, and 

 longicoUe. 



H The internal seminal vesicle is so extraordi- 

 narily large in Distomum variegatum. that it 

 exceeds that of the ovary and two testicles. 



Ij This cirrlms-sac, together with the penis, is 

 very long with Distomum lima, maculosum, 

 variegatum, and ovatum ; but it is especially so 

 with Aspidogaster conchicola, and Monoslomum 

 verrucosum. 



16 The protruding cirrhus or penis of Distomum 

 holostomum is provided with small bunches ; and 

 that of Monoslomum verrucosum with num- 

 berless little warts. 



1' 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. 



IS The common genital opening is usually sit- 

 uated on the middle of the neck, and with Dis- 

 tomum, it is directly in front of the ventral sucker. 



With Distomum clavigerum, and ovatum, it is 

 upon the sides of the neck, and with Distomum 

 caudate, and holostomum, exceptionably, it is on 



* [ § 115, note 12.] Thaer (Muller^s Arch. 1850, 

 p. 602, Taf. XXI. fig. 19) has described and fig- 

 11 



ured the spermatic particles of Pohjstomum ap- 

 pendiculatum, as Cercaria-form. — Ed. 



