56 



AN ELEMENTARY TEXT-BOOK OF BIOLOGY. 



is a straight tube, of varying calibre, traversing the whole length 

 ofjthe body, and separated from the body-wall by a spacious 



A B 



Fig. 18. DIGESTIVE AND CIRCULATORY ORGANS AND NERVOUS SYSTEM 

 OF EARTHWORM. A, Digestive and circulatory organs; b.p, buccal 

 pouch ; ph, pharynx ; >, oesophagus ; ce.gl, O3sophageal pouches and 

 calciferous glands; cr, crop; gz, gizzard; i, intestine; c.g, cerebral 

 ganglia; A, hearts; d.v, dorsal vessel. B, Nervous system ; c.g', cerebral 

 ganglia; c.c, circumcesophageal commissure; g.g, ganglia of ventral 

 cord; n, nerves, from ganglia; n', nerves, from between ganglia; *//, 

 sympathetic nerves. 



or body-cavity, which is divided into compartments corre- 

 sponding to the segments, and separated imperfectly from one 

 another by thin transverse partitions, the mesenteric septa, which 

 are perforated below. These septa are firmly united to the gut, 



