BY J AS. P. HILL. 31 



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 vSpengel 

 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 Ptychodfira, except Pt. 

 minuta and sarnlensiH, 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 l)ounded 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 jDoints 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 {gvy.) 

 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 Bodij : 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 al^dominal 

 region characterised by the j)resence of the two epidermal stripes 



