HAPLODISCUS PIGER. 
3 
(cf. fig. 4) ; but whether such nuclei belong properly to the 
muscle-fibres, or whether they are the remains of an ecto- 
dermal epithelium which has otherwise disappeared, I have 
been unable to determine. 
Beneath the layer of transverse fibres is a longitudinal layer, 
which appears to be much less important, its fibres being 
fewer and farther apart. These fibres seem in section to be 
connected with irregular, nucleated protoplasmic elements 
(fig. 4, m. ep.) } the distinction of which has been perhaps 
exaggerated in the figure. 
The only other muscles of the body are those round the 
ductus ejaculatorius (figs. 5, 7, and 10), where their 
structure is more easily seen. In this region every fibre 
appears to consist of a thin, wavy, contractile portion, often 
branched at the extremities, and connected near its middle 
with a granular protoplasmic body, containing a distinct 
nucleus. These fibres resemble those described in Taenia by 
Roboz more than any others with which I am acquainted. 
A protoplasmic tunic, perforated only by the ductus 
ejaculatorius, forms the innermost layer of the body wall, 
lying immediately beneath the cuticle dorsally, but separated 
from that structure on the ventral side by the muscles. This 
tunic (figs. 2, 3, 4, 10, P. t .) consists of an irregular layer 
of granular protoplasm, in which nuclei are embedded at fre- 
quent intervals, but which does not show any trace of division 
into distinct cells. From the inner wall of this tunic numerous 
processes are given off (figs. 2, 3, 4, 10, P. r.) which anasto- 
mose with one another in the cavity of the body, forming a 
reticulum which is either continuous with, or forms an invest- 
ment for, the remaining organs of the animal. 
Embedded in the protoplasmic tunic, and opening from it 
through the cuticle to the exterior, are numerous mucous 
glands (figs. 2, 3, gl.). These are irregular spaces in the 
tunic, filled with a deeply-staining, probably mucous sub- 
stance. The glands often contain, besides mucus, the remains 
of nuclei. 
The brain is a transverselyeiongated body, lying embedded 
