THE SEXUAL ORGANS. 



305 



such as Tcenia solium and Bothrioceplialus latus, whose branched 

 (Fig. 156) or rosette-shaped (Fig. 157) uterus was known to observers 

 as early as the beginning of the last century (since 

 Andry), although it was generally erroneously regarded 

 as an ovary until the time of v. Siebold. 1 



But though the sexual organs of the tape-worms 

 are thus very striking, their accurate investigation is in- 

 volved in great difficulty. It was, of course, soon agreed 

 that the proglottides were provided with male as well as 

 female organs, but the structure and the relation of the 

 various parts eluded for a long time further deter- 

 mination. We have, however, gradually obtained a 

 satisfactory insight into these, thanks especially to the re- 

 searches of v. Siebold, Sommer and Landois, 2 and myself. 



What stands in the way of the analysis of the sexual 

 apparatus of the Cestodes is partly the parenchymatous 

 nature and thickness of the tape-worm body, which 

 almost always necessitate a detailed methodical mani- 

 pulation, and partly also the complex structure and the .FIG. 156. Two 

 thick outline of the various parts. Besides this, the folium 1 ^th 

 form and structure of the latter often vary considerably branched uterus, 

 from those of nearly related species, and are influenced 

 in an unusual way by the external form of the joints, as will be still 

 more discussed in considering the Tseniadse. 3 



Proceeding to the general consideration of these sexual organs, I may 



FIG. 157. Female sexual organs of Bothriocephalus latus, showing the uterus, ovary, 

 shell -gland, and yolk-gland, (x 12.) 



1 Concerning the historical development of our knowlege of the sexual organs of the 

 Cestodes, compare especially the statements of Sommer, Zeitschr. f. wiss. ZooL, Bd. xxiv., 

 p. 299, 1874. 



2 Besides the formerly mentioned treatise on Bothriocephalus, Sommer's later work on 

 the structure and development of the sexual organs of Tcenia mediocandlata and T. solium 

 (Zeitschr. /. wiss. ZooL, Idc. cit., supra) deserves special mention. 



For comparison with the original descriptions given by Sommer and myself, chiefly 

 of the common bladder- worms, I may refer to the data furnished by the following investiga- 



U 



