184 WHEELER. [VoL. 1X. 
supposition, I find no connection between the oviducts and 
the uteri. 
Bdelloura and Syucelidium appear to be the only Triclads 
which have two uteri and a distinct duct and opening for each 
uterus on the surface of the body.!. The gap between these 
ectoparasitic planarians on the one hand and the fresh-water 
and land planarians on the other, is partially bridged by a 
series of forms representing the gradual emancipation of the 
oviducal opening from the duct of the uterus (vagina of 
authors).2, In the land Triclads and in Gunda lobata (O. 
Schmidt) the oviducts unite with the hind portion of the uterus ; 
in Haga plebeja they open into the lower end of the uterus; 
in Gunda segmentata and G. wlvae the unpaired portion of the 
oviduct opens into the duct of the uterus; in the common 
fresh-water species it can hardly be said to open into the duct 
of the uterus, but has a separate opening into the genital 
atrium. In all these forms, however, the duct of the single 
uterus opens directly into the genital atrium; in Sdelloura 
and Syucelidium the ducts of the ¢zwo uteri appear to have no 
connection with the oviducts and are entirely removed from the 
genital atrium. I fail to find any traces of yolk cells or ova in the 
uteri and I have seen nothing to indicate that the egg-capsules 
are formed in these organs. Spermatozoa are nearly always 
present in considerable quantity. In a specimen of Bb. can- 
dida | found spermatozoa in either oviduct for some distance 
up towards the ovaries. In a specimen of Syucelidium I 
found an egg about to be discharged into the genital atrium. 
These few observations are calculated to render the vexed 
question of the function of the uterus in Triclads still more 
perplexing. The great variation in the position and shape of 
the uterus —in other words, its morphological instability — in 
Triclads points to considerable variety of function. For the 
present I am inclined to believe that the uteri of Syuce@lidium 
1 Unless, indeed, this latter peculiarity obtain also in Bergendal’s Uteriporus 
vulgaris. I have not seen his description of this form, but I conclude that its 
single uterus has an opening on the outer surface of the body from a remark in 
his recent paper (’92 p. 313). 
2 What I have called the vagina in Syxcelidium is not, of course, homologous 
to the vagina of other Triclads. 
