Cyathooormus mirabilis n. g., n. sp. 



23 



Text-fig. 3. 

 Two zooids placed side by side 

 to stow the difference in the course 

 of intestine. 



zooid in the colony. In those zooids 

 situated on the left side in a pair of rows 

 the rectum turns to left and terminates 

 in the anus without crossing the oesop- 

 hagus. In those belonging to the right 

 half of a pair of rows, on the other hand, 

 the rectum turns to right and crossing the 

 oesophagus on its dorsal and right side, 

 opens into the longitudinal furrow lying 

 next it on that side (see textfig 3). 

 That the intestine lies mainl^^ on the 

 left side of the stomach in either case 

 is clearly seen in a cross section through 

 the lateral wall of the colony (PI. I., fig. 3). 



The intestine, with the exception of the duodenum, is nearly 

 of the same width through its entire length. Its diameter is a 

 little less than that of the stomach, but is greater than 

 that of the posterior end of the duodenum. The relative sizes 

 of these parts are shown in PI. III., figs. 15 and 16 (st.^ d., 

 int.) For the greater part of its length the intestine is smooth 

 walled, exhibiting only slight wrinkles at the place of bending and 

 in the terminal region just in front of the anus. The wall of the 

 intestine is lined with low columnar cells with the nuclei situated 

 near the base, and is, in comparison with that of the stomach, 

 considerably thinner. A glance at PI. III., fig. 20, representing a 

 cross section of the abdomen, will suffice to make clear the 

 difference in the thickness of wahs of these organs. On the lips 

 of the anus, however, the cells are taller. At the anal opening 

 the wall of the rectum is turned outwards so as to form a sort of 

 lip (PI. III., fig. 17). Just in front of the anus the rectum is 

 surrounded by a set of ring muscle fibres which no doubt perform 

 the function of a sphincter. 



In the middle third of its course the intestine is embraced 

 externally by a system of fine branching tubules, corresponding to 

 the digestive gland found in many simple ascidians. The duct 

 from this system runs across from the intestine and opens into the 



