ANNDLATA. 233 



continued straight to the anus. Through the whole length of the 

 intestine, cfccal processes are sent off on each side, to the number of 

 about twenty pairs. They commence of a slender diameter, but gra- 

 dually enlarge, send off many short branches, which subdivide, and 

 terminate in fusiform pouches. These productions of the intestinal 

 canal are homologous with the gastric caeca of the leech ; but they 

 are more isolated from the common canal, and more distinct in their 

 functions. It is thought that the chyme passes into them, and that 

 the chyle is separated from it by a secretion of the terminal cajca 

 analogous to bile. Hunter has placed a preparation* of them at the 

 commencement of his series of hepatic organs, as one of the early 

 forms of that system. 



The more unequivocal form of hepatic organ is that yellowish 

 or brownish glandular mass which surrounds almost the whole 

 intestinal canal in most Anellides, and which consists of a^gresated 

 follicles, opening either singly or by a duct common to several, upon 

 the inner surface. These follicles give a villous character to the 

 outer surface of the gut in Enchytreeus ; their homologues form the 

 part called " chloragogena " by Morren in the Lumbricus. In Am- 

 phitrite the follicles are of a bright yellow colour. 



The abdominal cavity is obliterated in the suctorial Anellids by 

 the spongy vascular tissue uniting the sacculated alimentary canal 

 to the skin: in the Terricola it is divided into numerous small com- 

 partments by the septa, which closely connect the intestine with the 

 skin : it is also more or less subdivided by the incomplete septa and 

 the muscles of the setigerous sheaths in the higher Anellides ; but 

 all the recesses and ramifications of the abdominal cavity intercom- 

 municate freely with each otlier. In this complex space there is a 

 colourless fluid containing organic corpuscles, which is kept in 

 constant motion by the varying contractions and dilatations of the 

 surrounding segments, a ciliated epithelium being rarely present, as 

 e.g. in Aphrodita aculeata ; or only partially developed upon the 

 peritonaeum, as, e. g. in the part lining the tubular feet of the Her- 

 mellaef, and the hollow branchiae of the Ghjcera. This fluid answers 

 to the chylaqueous fluid of the Radiata.i In the Errantia it performs 

 one of the functions of an internal skeleton, acting as the fulcrum or 

 base of resistance to the cutaneous muscles, the power of voluntary 

 motion being lost when the fluid is let out ; the vermicular motions 

 of the intestine are aided or determined by its resistance and support ; 



* No. 782. t CXC. p. 36. 



X Tb. pp. 170 — 173., ^vhcrc different forms of the chylaqueous coi-pusclcs are 

 described. 



