55 



that the extension is effected by the attachment of the suctorial base of the stalk to the wall 

 of the coenoecium, the animal then crawling on its buccal disc away from its fixed end. 



The second stomach of C. levinseni (figs. 33, 34, stonir) is more ^'^shaped than in 

 C. dodecalopJms. But a comparison of these figures with fig. 42 (C. dodecalopJuis) will shew 

 that there is no essential difference, in this respect, between the two species; and it is not 

 impossible that a less contracted specimen of C. dodecalophus might have its second stomach 

 more in the position which appears to be characteristic of C. levinseni. In the latter the second 

 stomach forms a considerable portion of the bend of the fZ-shaped tube, being about equally 

 developed on both sides of the actual bend. Examination of entire specimens (fig. 6) shews 

 that the folds of the second stomach are arranged in a spiral line, and it might indeed be 

 said that they constitute a spiral valve. The two limbs of the alimentary canal are, as usual, 

 separated from one another by a part of the third body-cavity (<5. ^.'(5.), subdivided by a median 

 partition (PI. XI, fig. 130, ines?~) which must be regarded as part of the dorsal mesentery. The 

 cavity of the rectum is usually large, and commonly contains a large mass of faeces, in which 

 the remains of Diatoms may be distinguished. In several of the specimens (as in the one shewn 

 in fig. 34) a quantity of these faeces is passing out of the anus, which accordingly appears 

 widely open. 



The alimentary canal of C. gracilis is shewn in fig. 37. The second stomach leaves 

 the stomach at the end of its main axis, as in C. levinseni, and forms a wide cavity which 

 extends on both sides of the bend of the alimentary canal. The third body-cavity passes, as 

 usual, between the two limbs of the second stomach, but the space shewn in fig. 37 between 

 the stomach and the intestine is not lined by peritoneum and is probably an artefact. 



My examination of the alimentary canal of C. sibogae (neuter forms) has been complicated 

 by the unsatisfactory state of preservation of the material. Sections of the mass of zooids still 

 contained in the basal coenoecium were not satisfactory; and it was very difficult to isolate 

 zooids in an uninjured condition. My results indicate, however, a great elongation of the 

 alimentary canal in the adult and uncontracted zooids. In fully extended specimens (fig. 38) 

 the second stomach appears to pass off from the extreme ventral end of the elongated stomach, 

 and the form of the entire canal is thus more simply ^/-shaped than in any of the other species. 

 Fig. 40, taken from an entire specimen, shews a condition which is jjrobably due to contraction 

 of the body, the bend of the canal being reflected towards the anterior side of the stomach 

 In the uncontracted condition of this specimen it is probable that the position of the second 

 stomach would have been as in fig. 38. 



The structure of the mouth and pharynx of Cephalodisctis require a somewhat detailed 

 description, which may be preceded by one or two remarks on that of the remaining parts of 

 the alimentary canal, and on the nature of the food. 



The structure of the oesophagus resembles that of the pharynx, of which it is indeed 

 merely a division. But it is always to be recognised, in suitable preparations, and hence deserves 

 a special name. It is probal)ly a sort of ante-chamber to the stomach, through which food 

 pas.ses by definite swallowing actions when a sufficient quantity has accumulated in the pharynx. 



