19 
insofern er eine Verbindung zwischen der Einmiindungsstelle des 
Uterus in den Eiergang einerseits und der Aussenwelt andererseits 
darstellt, einigermaassen an den Laurer’schen Canal der Trema- 
toden und Cestoden.“ I will discuss his interpretation of the function 
of this canal later. In niy treatise on the terminology of the geni¬ 
tal apparatus in PolycladS (Bock, 1913), I introduced, as already 
mentioned, the name ductus vaginalis for this canal. 
Verri 11 (1893) mentions two species of the genus Trigonoporus 
from the New England coasts; Tr. folium and dendriticus. The 
former was already described in 1873 as Leptoplana folium. „In 
the structure of the reproductive organs, and especially in having 
two orifices for the female duet, these species both agree well 
with the type species of Trigonoporus.'' (1893, p. 489). About 
T. folium he says: „The anterior female pore is near the male 
orifice, and in some specimens, owing to contraction of the tissues, 
both are brought close together into a single pit-like depression; 
the dorsal portion of the female duet is somewhat elongated, and 
its posterior opening is at a considerable distance from the anterior 
orifice; the ventral part of the duet is shorter and broader, and it 
receives the duets of numerous shell-glands; at its upward bend it 
is considerably dilated, and this part probably serves as a sperma- 
theca. Behind the second female orifice there is usually visible 
a siender median duet which appears to terminale in a minute 
median pore; this is, perhaps,’the central nephridial duet, but its 
extension forward could not be traced in the preparations.“ Figures 
from the mounted specimens are reproduced on his Plate 44, 
Figs. 6 and 7. All that is said about the female organs in T. den¬ 
driticus (Plate 44, Fig. 3) is that „the anterior female orifice is a 
little distance back of the male orifice; the glandular part of the 
vagina is elongated, and its posterior orifice is situated well back.** 
When the Identification of the entire structure of the genital 
apparatus is, as in this case, exelusively made on a mounted spec- 
imen, it is always a little unreliable. 
It should be emphasized here that no „central nephridial duet** 
is known in PoIyclads, and therefore, it seems very likely to me 
that this duet belongs to the female apparatus. On his figures 
(Plate 44, Figs. 6 and 7) it can be seen running forward to the 
posterior female opening mentioned. A sectional examination of 
2 * 
