366 
S. .1. JOHNSTON. 
Oil the surface of the process through a long duct which runs 
between the longitudinal muscle-fibres. Just at the tips of 
the processes the muscular layers are much reduced^ and the 
gland-cells seem to have converted their entire protoplasm 
into mucus and rhabdites (fig. 4). Lying in the middle of 
the parench^una of the process is a large space surrounded 
by a very definite muscular layer^ as well as several smaller 
cavities. With the central space in each process a large 
branch given off from the excretory vesicle communicates 
(fig. 22). Fluid forced into this channel from the excretory 
system apparently takes part in the protrusion of the process, 
and^ together with the action of the muscular system of the 
process, would render it tense. 
These processes, according to Taylor, who found them, do 
not seem to be used in any way for attachment. The function 
of rhabdites in the flatworms seems to me to be obscure, no 
very satisfactory explanation having been offered for them. 
In this case they probably give a certain amount of stiffness 
to the secretion of the processes, and may have an irritating 
effect. The whole organ is most probably used for cleaning 
up an area of the wall of its host’s intestine, so as to make 
a place to which the sucker can be effectively applied. 
Muscular System. — The muscular layers of the body- 
wall are very strongly developed. A complete layer of 
circular fibres lies immediately adjacent to the cuticle ; within 
the circular is a thick layer of longitudinal fibres, and internal 
to this is a layer of diagonal fibres, somewhat thicker than 
the outer circular layer. A dorso-ventral system of large 
muscle-fibres is developed to a very marked extent (figs. 
15 and 16). The majority of these are fairly perpendicular 
to the dorsal and ventral surfaces of the body; many, however, 
are oblique in their direction. At each end, at the point 
where they reach the level of the diagonal fibres of the body- 
wall, these dorso-ventral fibres become divided into a number 
of branches, so that the area of their insertion into the cuticle 
is very much greater than the area of the cross-section of the 
fibre. 
