11. L. M. PIXELL. 
2 '36 
'File oesophagus {(es.), with its thick walls often much 
folded, ouly extends for a short distance. Fig. 2 is a ti'aiisvei-se 
section through its posterior part where the two branches of 
the lateral vessel have just united. 
'J'his is followed by the pregastric region (Fig. 3, gas.) 
(“preestomac” of Selys Lougchamps, Vormagen of Cori) which 
has a large cavity irregular in shape with thin walls. The 
e]hthelium is cubical, ciliated, and has oval nuclei. Along 
the postero-niedian regiori close to the afferent vessel is a 
longitudinal band of epithelium (Fig. 3, c. h.) thicker than 
the rest and with several layers of elongated nuclei. This 
has been described in P. pacifica (Torrey [15]) and in P. 
architecta (Andrews [1]), but is veiy little developed in 
l^h. hippocrepia. 
The stomach (Fig’. 4, st.) is the large terminal i-egion of 
the descending pai t of the tract situated in the ampulla. It 
has a thick epithelium with ovoid nuclei. Oii the postero- 
median side there is a longitudinal groove directly con- 
tinuous with the thickened band in the pregastric region -and 
having similarly sevei al la 3 ’ers of nuclei which stain more 
deeplv than the ordinary ones (Fig. 4, gr.). The cells along 
this groove have very long cilia, d’he digestive a.reas which 
carry on intra-cellular digestion (Fig. 4, d. a.) have no cilia, 
and the free ends of the cells are distinctly amoeboid during 
functional activitx'. The whole of the ascending limb of the 
alimentary canal is called the intestine except for the very 
short part contained in the anal papilla, which Cori considers 
to be a proctodaeum and calls the rectum. The part of the 
intestine in the amjmlla (Fig. 4, ’mt.), the onl}" part called 
“ intestine’’ by Benham, has thick, closel}' ciliated walls and 
generally an oval lumen. The epithelium is c^diudrical, with 
oval nuclei. The upper part of the intestine (hgs. 2 and 3, 
int.), has cubical epithelium, with long cilia and large nuclei. 
In transverse sections the intestine appears oval or elongated, 
only occasionally showing the usual triangular shape due to 
the pull of the three mesenteries. 
The cells in the lower part of the stomach and intestine 
