4115. 



THE HELMIXTHES. 



121 



The neck of the Internal seminal vesicle [Veslcida seminalis i7iterior), 

 <lischarges its contents at this same place into the uterus, through a special 

 Vas defereyis from one of the testicles. The Uterics connnences as a narrow- 

 tube, which may be regarded as a Tuba Fallopii. Its dilated portion, 

 VA'hich 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 semi?ialis iiiterior .'•^^^ 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 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 

 tw^o organs are located at the anterior extremity of the body, and only in 

 Holostomum, and Gasterostomum, are they removed to the other extrem- 

 ity. ^^s> 



8 The length of the uterus varies very much in 

 different genera and species, and its coils are 

 always irregular. With Monostomwn mutabile, 

 and verriicosum, the oviduct arising in the poste- , 

 rior extremity, passes in front with numerous 

 transverse coiJs. 



y I have found one testicle only, in Amphisto- 

 snum subclavatum, and Aspidof^asler conchicola, 

 altliough I have seen three or four in Distomum 

 appendiculatum, and cy^noides. 



10 With Distomum ovatum, the two testicles are 

 side l)y side behind the ventral suclier ; with Dis- 

 tomum chiloxtomum., they are on each side of this 

 sucker, and witli Distomum craxxum, mihi (from 

 the intestine of Hirundo domestica)^ they are in 

 .front of it, on each side of the neck. 



11 With Distomum Innsicolle, lanceolatum, 

 oxyurum, echinatum, globiporum., and Amphis- 

 tomum conicum, the testicles have many depres- 

 sions ; see Bojanus, Isis, 1821, Taf. II. fig. 25-27 ; 

 Burmeister and Sielio/d, in IViesmann's Arch. 

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

 I)e Ampliistorao conico. fig. 21, 24, 25. With 

 Amphislomum subtrii/uelrum, sinanteum, and 

 Distomum /lians, the number and depth of these 

 dei)ressions gives the testicle the aspect of a bundle 

 of caeca ; see Bojanus, loc.cit. Taf II. fig. 14-17, 

 and Diesing Ann. d. Wiener >Ius. I. Abth. 2, 

 Taf. XXII. 



12 In the testicles of the Trematodes, the devel- 

 Of)ment of the spermatic particles occui's after the 

 usual m(xie. 



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 unless they are quite isolated. When 

 put in water they become twisted together, and 

 assume a loop-like arraugemeut, — their motions 

 instantly ceasing. 



For the development of the spermatic particles 

 of the Trematodes, see KoUiker, Die Bildung du 

 Saamenfäden in Bläschen, loc. cit. p. 44, fig. 31.* 



13 These two vasa deferentia are sometimes 

 blended together before reaching their destina- 

 tion ; this is so in Disto?num 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 Distomum /ima, macu/osum, 

 variegatum, and ovatum ; but it is especially so 

 with Aspidogaster conchicola, and Monostomum 

 verrucosum. 



1Ö The protruding cirrhus or penis of Distomum. 

 holostominn 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 wiih Dis- 

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



With Distomum clavigervm, and ovatum, it is 

 upon the sides of the neck, and with Distomum, 

 caudate, and holostomum, exceiJtianably, it is oa 



*[§ 115, note 12] TAner (7»/«//«?-'.? Arch. 1850, ured the spermatic particles of Po/j/.^/omuw ap- 

 p. 602, Taf XXI. fig. 19) has described and fig- /je«(/(ct(/«i»m as Cercaria-form. — Ed. 

 11 



