STUDIES ON THE ECTOPABASITIC TEEMATODES OP JAP AX. 89 



fig. 8 ; PI. XXIV, figs. 6, 9, & 10 ; PI. XXV, figs. 1, 3, 5, 8, & 9). 

 It then proceeds either staight forwards or else a little to the left, 

 makinff all the while numerous small but close convolutions : and 

 then turning more or less towards the right on the dorsal side of the 

 penis, enters the latter close to its base. Here it forms a swelling, 

 the vesiciila scminalis, and then again contracting to a very small canal 

 and traversing the penis parallel to its central ca^'ity, opens finally 

 into this at some distance fi-om its apex, in some species on the top of 

 a papilla (PI. XXII, fig. 4).'' 



St.-Remy^^ distinguishes in Tristomum three portions of the 

 vas defei-ens, viz., (1) the single " canal seminal," (2) the " vesicule 

 ejaculatrice " situated in the penis and receiving at one of its ends the 

 nari'ow termination of the seminal canal and continued at the other 

 into the (3) " canal ejaculateur," with which it communicates by a 

 very short, iiarrow canal. It does not, however, seem to me necessary 

 to distinguish these parts. As I have mentioned above, there are 

 numerous constrictions in the course of the vas deferens ; but these 

 are quite iiTegular, and can not, in my opinion, be taken as marking 

 off distinct portions of , the vas deferens from each other. It 

 is, however, convenient to designate that portion of the vas deferens 

 which lies within the penis the ductus ejaculatorins, although it should 

 be remembered that in many species this is not the only portion that 

 is concerned in ejecting the sperm fluid. In Tristomum and Epibdella, 

 this portion is provided with circular muscular fibres (PI. XXII, fig. 

 4 ; PI. XXVI, fig. 7). 



In Epibdella a short vas efferens proceeds from each testis ; but 

 soon unites with its fellow and forms a single vas deferens. This 



1). For minuter details see the description of species. 



2). Gr. St.-Remy— Contribution a retudedel'appareil genital ohezlesTristomiens. Archives 

 de Biologie, T. XII, 1892. p. 5 et infra. 



