ARENICOLA. 185 
hold the front part of the alimentary canal in position. 
There is no dorsal nor ventral mesentery, but in the “tail” 
region, from segment 20 backwards, there are regular trans- 
verse ‘septa. Hence the alimentary canal, from segment 4 
to segment 19 inclusive, is free to move in the ccelom. 
The pharynx leads into a_long esophagus which widens 
out into the stomach. Just before the commencement of 
the latter there is a pair of esophageal glands 
or pockets, the lumen of which opens into the 
cesophagus. They are probably digestive glands. The 
ay Alimentary. 
Fig. 112,—TRANSVERSE SECTION OF ARENICOLA (Diagrammatic). 
Dorsal Blood-vessel receiving Efferent Branchial. 
Gill (1-6). 
Cay 
Branchial. 
Efferent 7 
Branchial. . Oblique 
Muscle. 
Afferent : 
Branchial. #” ~- Longitudinal 
Muscle. 
Circular Muscles 
é ; - Co with Ectoderm 
Ventral Vessel.’ on at. re and Cuticle 
ge GP outside, 
On the left is seen the arrangement of the first six branchial segments ; on the right the last seven. 
stomach is wide, and is covered with yelJore-cel/s, intersected 
by a network or plexus of blood-vessels. At about the level 
of the seventh pair of gills the stomach passes into the 
intestine which terminates in an anus. ; 
Arenicola is perpetually employed in passing quantities 
of sand and food-particles through its alimentary canal, 
digesting the latter and egesting the former. 
