1898-99.] Dr 0. Fuhrmann on Prosthecocotyle torulosa. 645 
genital canals pass out. They go through the strobila without 
diminishing in thickness at the limits of the segments. This 
muscular layer, which has a thickness of 0‘03S mm., touches the 
cuticula only at the limits of the segments, and it follows from 
this disposition that the external parenchyma of each segment is 
completely separated. The external muscular layer is much more 
powerful. It consists of bundles (diameter QT14 mm.) formed by 
fifty fibres at the utmost. This stratum of longitudinal muscles 
is separated from the external layer by a small zone of parenchyma, 
and only interrupted for a short space on both sides of the strobila. 
Inside of the longitudinal muscles we find a layer of transverse 
muscles. In the lateral part of the strobila these muscles radiate 
only in the external parenchyma, and fix themselves on the 
cuticula of the anterior side of the segments. The dorso-ventral 
fibres are specially situated where they are not disarranged by the 
development of the genital glands, and are therefore mostly found 
in the lateral sides of the proglottis and between the different 
segments. These fibres can, without doubt, modify the depth 
of the incision between the segments. As to the form of the 
fibres, we find it differs in the different systems. The dorso- 
ventral fibres are very long and fine. The transverse fibres are 
also very long. The longitudinal fibres are, on the contrary, short 
and thick. 
We could only study the water-vascular system in the strobila. 
The two pairs of longitudinal vessels are placed one above the 
other ; the dorsal one has a diameter of about 0 01 mm. ; the ventral 
one is much better developed, and is 0'06 mm. wide. The vessel 
that joins the ventrals has a diameter of 0’032 mm. The water- 
vascular system has a very peculiar structure, the vessels having a 
powerful musculature which transforms this system into a con- 
tractile organ. The dorsal vessel is especially muscular, and thus 
varies much in size. On the ventral vessel the circular and lonni- 
O 
tudinal fibres are neatly developed, but each one is represented 
by a simple stratum. Such a complex musculature has never 
been noticed in the water- vascular system of the cestodes. 
Riehm * has described circular muscles on the vessels of Dipy- 
* Biehm, G. , “ Studien an Cestoden,” Zeitschrift f. d. ges. Naturwiss 
Bd. 54, pp. 545-610. 1881. 
