INTRODUCTION. 



XXI 



pharynx ; and in this case the dark-coloured hepatic cells 

 range for some distance above the stomach on the walls 

 of the tube, the lower part of K 8- Tii - 



which may therefore be re- 

 garded as in some sense an 

 extension of the digestive sac 

 ( = the " cardiac cavity ") . 



In the oesophagus transverse 

 striae are distinguishable, which 

 are muscular in character; 

 and to their action in com- 

 pressing the walls the peristal- 

 tic movements are due*. 



The stomach, in its simpler 

 form, is a sac or bag, with 

 rather thick walls (Woodcuts, 

 figs. i. & viii. st), often wide 

 above, and more or less pointed 

 below; sometimes elongate and 

 almost cylindrical in shape. 

 It is coloured a rich yellowish 

 brown, the colour being due 

 to the presence of numerous glands on its inner or lining 

 membrane, which secrete a brown fluid, and probably 

 discharge the functions of a liver ; this fluid mingles freely 

 with the contents of the stomach, and imparts its own 

 colour to themf. 



Hyatt, op. cit. p. 48. 



t According to Vogt, these cells are not only biliary in function, but also 

 act as absorbent*. In polypides (of Loxosoma) that had been fed with car- 

 mine, he lias seen them assume an orange or scarlet tint, showing that there 

 had been an absorption of the colouring-mat tor, which had modified the or- 

 dinary amber-yellow of the cells. " Sur le Loxo&onie des Phascolosomes," 

 Archives de ZoologU exptrimentale, 1877. 



Beania mirabilis. 



