STUDIES OX 'I'lTE EO rOPATîASTTir' TREISFA'l'ODES OF .TATAX. \27 



In }fon(i('nhili', Tn'shniiinii. nnd F.jiihdcJIii tlie vngina is present 

 oiilv on tlio left side of tlie hody. ;uid opens to the extei'ior on 

 tlie ventral surfiu'c In Moiiocutijlc tlie vaa'innl oj)ening is situated 

 close to the left" trunk of the intestine, about midway Ijetween the 

 pcmix iii'iiiltills rininiiniu's and the anteri<3r end of tlie ovary, and is sur- 

 rounded hv a comjiact tissue exactly similar to that described in J fixaco- 

 iijlf : but there are rio muscnlar fibres (PI. XVII. fiu'. 1). Ir leads 

 into a short canal which soon opens into a laru'e spherical cavitv, the 

 rcci'jii(tcuJuiu sciiiltu's ; from the other end of this a canal proceeds 

 backwards, and opens into the oviduct at the ])oint where the 

 latter receives the paired yolk-ducts. In Tn'shnninn tlie vaginal open- 

 ing is situated a short distance behind the opening of the genital atrium, 

 in some s])ecies more towards the lateral margin, but in others nearer 

 the middle line. In most s])ecies the opening is surronnch'd more or 

 less with tlie compact tissue so often mentioned in other genera ; bnt 

 this is in most species very inconspicuous. The vaginal canal makes 

 in this genus numerous complicated windings in its course; 

 and at various distances from the external opening according to 

 the species it is swollen to a cDnsiderable size ;uid is filled with 

 S])erm mass — forming the rrc/'jitnciiJinii s('iii/nis. lîeyond this the 

 vaginal canal conti'acts into a vcrv tine canal, which then o|)ens in all 

 the species I have ol)served into tlie yolk rescrv(^ir (PI. XXI, hg. <S; 

 V\. XXII, fig. 5; PI. XXirr, tig. 8,- pi. XXV, hg^. 3, -S, & S). and 

 not into the oviduct as is stated Ijy Monticelli" to be tlie case in 

 Tn'sf. uncinatiim. 



From the above it is evident tliat the seminal receptacle in 

 Trisfomum and Monocoliilc is nothing else than a part of the vaginal 



1). Monticelli— Trist-oinnin uni'iuatuui, n. sp. Boll. d. Soo. ili. Nat. iu Xapoli. An. TIT, fasf. 

 IT, 1889. 



