BY JAS. P. HILL. 
3 1 
cells lining the gut. The cells of the liver gut possess distinct 
cilia, and in accurate sections through its lining epithelium which 
are met but seldom, the outer surfaces of the cells form a sinuous 
line, and no vacuoles are visible in them, so that, as Spengel 
remarks, the vesicles he has observed in them are probably the 
result of the action of reagents. On the outer side of the epithe- 
lium of the liver sacs and the gut wall there is a rich system of 
capillary vessels. As in other species of Ptychodera, except Pi. 
minuta and sarnienxis, two ciliated grooves are present in this 
species, and they show the usual structure. Each consists of a 
special ciliated band of long columnar cells sunk below the level 
of the gut epithelium and bounded on its dorsal or median side 
by a projecting conical mass composed of elongated cells, the 
"covering pad." 
The ciliated grooves extend for a considerable distance into the 
genital region proper, and they are there situated somewhat below 
the points of attachment of the lateral septa to the gut wall, and 
are separated from the epidermis by the thick layer of longitudinal 
musculature. Posteriorly, about the middle of the hepatic region 
where the liver sacs are largest, the genital wings are reduced to 
mere ridges, overhung by the outwardly extended ends of the liver 
sacs. In fig. 24, the left half of a section about the middle of the 
hepatic region is represented, and the ciliated groove (cgr.) is seen 
to lie just below the outer wall of the reduced genital wing (gw.) 
and now quite close to the epidermis, being separated from it only 
by a thin layer of the longitudinal musculature which becomes 
thinner just at this point. The genital wings can be traced as 
mere elevations of the epidermis below which the ciliated grooves 
are situated to near the posterior end of the hepatic region. 
Hind Body : The course of the ciliated grooves behind the 
hepatic region is marked externally by two longitudinal epidermal 
stripes which, commencing laterally to the posterior small liver 
sacs, extend over the anterior two-thirds of the hind-body region. 
The hind body can thus be divided into an anterior abdominal 
region characterised by the presence of the two epidermal stripes 
