INTRODUCTION. 



XXI 



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

 range for some distance above the stomach on the walls 

 of the tube, the lower part of Fig. vii. 



which may therefore be re- 

 garded as in some sense an 

 extension of the digestive sac 

 ( = the " cardiac cavity ") . 



In the oesoj)hagus transverse 

 striae are distinguishable, which 

 are muscular iu 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 yello^\dsh 

 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 stomachy and imparts its own 

 colour to themf. 



* Hyatt, ap. cit. p. 48. 



t According to Yogt, these cells are not only biliary in fimction, but also 

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

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

 liad been an absorption of the colouring-matter, which had modified the or- 

 dinai-y amber-yeUow of the cells. — '• Sur le Loxosome dcs Phascolosomcti" 

 Archives de Zoologie experimentale, 1877. 



Beania mirabilis. 



