56 
consideration is, consequently, when in an inactive position, directed 
sHghtly forward, although the hook-shape of the fleshy part of 
the penis characteristic for all Prosthiostomids 
is well marked. The penis stylet is only 120 
long and reaches its maximum width, 6 i-v, in 
its middle part where its walls are thick. 
Towards the apex it becomes as thin as a line. 
The lumen of the stylet was filled with prostatic 
secretion. In its distal half the sheath of 
the penis is equipped all around with a high 
prostate epithelium and underlying embedded 
giand cells as in the genus Prosthiostomum. 
Only in Pr. lineatum Meixner does the secretory 
epithelium form a caudal half-circle. 
The two muscular accessory vesicles show 
pronounced deviation from the general type. 
They are very small (text-fig. 16), and have a 
dub shape, in direct contrast to the large, 
spherical, and exceedingly muscular vesicles of 
the Prosthiostomum-s\)Qc\Q^. The thin muscular 
Wall (measuring only 8 ^ in thickness) does 
not, as is usually the case, contain any nuclei 
in the fibrous layer. The efferent duet is here 
only a direct continuation of the vesicle. The 
muscular envelope of the vesicle merges into 
the musculature of the duet; the muscularis 
diminishes in thickness and at the same time 
the longitudinal fibres of the vesicle gradually 
disappear. In the Prosthiostomum-s^QCiQS, on 
the other hånd, the efferent duets, enveloped 
by their own special muscular covering, pierce the thick muscular 
Wall of the.vesicle. Whereas the efferent duets in the Prosthi- 
ostomum-spQcies are long and coiling,*) they are in the present 
case very short and almost straight. 
The seminal vesicle is, when seen from the ventral side, circular 
*) Pr. sin gular e Laidlaw 1904 is claimed to have „accessory vesicles“ re- 
latively small and their duets short. This species is supposed to lack 
cerebral eyes! 
Text-fig. 16. Euprosthi- 
ostomum adhærens. 
Middle part of a 
specimen, cleared in 
cedar-wood oil. In 
ventral aspect. 88x. 
av, accessory vesicles 
of the maleapparatus, 
ph, pharynx; php, 
pharyngeal pocket; 
vs, vesicula seminalis. 
