184 ANNULATA. 
dorso-laterally and are beautifully branched delicate organs 
of respiration. Through their thin walls the blood and 
outside water interchange carbonic acid and oxygen. The 
posterior part (3) consists of a great number (about 30) of 
Fig. 111.—A MaGNIFIED GILL-SEGMENT OF ARENICOLA. 
(After AsHworTH and GAMBLE.) 
Notopodial Sete. 
Branches of Gills. ¢ 
f 
Annulus. 
Nephridiopore. Torus Uncinatus 
(Neuropodium). 
compressed segments, on none of which are there any 
appendages or gills. 
The body is covered by a fine but definite 
cuticle secreted by the simple underlying ecto- 
derm in which there are unicellular glands. 
If the animal be cut open down the median dorsal line 
the whole internal anatomy is exposed, for Avendcola is a 
ccelomate animal and all the internal organs lie in contact 
with the ccelom. 
The ccelom is spacious, as in Polygordius, but it is not 
completely divided up into compartments. The front part 
is divided by three transverse sef/a2,* between the 
first, second, third and fourth segments, which 
Integu- 
mentary. 
Colom. 
* The first septum has a pair of hollow septal pockets which are muscular, and 
probably assist in protrusion of the pharynx. " 
