57 
but in median sagittal sections egg-shaped with its narrower end 
directed forward. The ductus ejaculatorius has a muscular wall 
not much thicker and only a little wider than the efPerent duets 
of the accessory vesicles. A peculiar faet is that the two seminal 
eanals open into the fronto-lateral part of the vesiele. As a result, 
one finds three tubelike eavities lined with epithelium, so that 
the lumen of the vesiele assumes the shape of a fork with 
three prongs, the middle of whieh eontinues as the duetus 
ejaeulatorius. Eaeh large seminal eanal is expanded nearest the 
seminal vesiele and equipped with an exeeedingly sparse epithelium. 
This short part is direeted forward. At a distinet boundary the 
epithelium then ehanges both appearanee and funetion. It is now 
made up of high, wide eells, and some of these eontain a large, 
round, homogeneous eorpusele that stains with eosin. Sueh an 
albuminous eoagulation, during the life of the animal in form of 
drops, has elearly a nutritive funetion and is emptied into the lumen 
of the seminal eanal. Aeeordingly we find here numerous seattered 
„drops'* or even large masses of them together with sperma. The 
latter are extremely short and often arranged in bundles. I must 
neeessarily point out that the eoagulations in the large seminal 
eanals resemble so greatly in their appearanee the large round 
eontents of the intestinal eells that I am unable to distinguish 
between them with the aid of the mieroseope. 
Text-fig. 17 shows the female genital apparatus. The forward 
direetion of the proximal part is an unusual feature. In this respeet 
we find an agreement with Enchiridium. Prosthiostomum-spQcxts, 
as well as other Cotyleans, have usually a vagina eurved eaudal- 
wards. Pt. pulchrum Boek, lineatum Meixner, and angustum Boek, 
form a series of transitory types from the ordinary Cotylean type 
of vagina (e. g. in Pr. siphuneulus) to the one in question, whieh 
thus is a seeondary manifestation. The eaudal direetion of the 
proximal part of the vagina is otherwise a feature praetieally gene¬ 
ral for the anatomy of Polyelads. Even sueh Aeotylean Polyelads 
whose female gonopore is situated near the posterior margin of 
the body present sueh a feature. This shows with what amazing 
tenaeity eertain apparently unimportant eharaeteristies manage to be 
retained. As far as I ean aseertain, Stylochocestus gracilis Laidlaw 
1904 is, if Laidlaw’s figure really is aeeurate, the only exeeption 
