320 ALFRED GIBBS BOURNE. 
the body-wall, but those which serve to retract this pad are 
much stronger than any of the others, and are attached as far 
back as the wall of Segment vir. The cesophagus really opens 
into the ventral wall of the cavity of the pharynx, so that this 
latter might be regarded as a diverticulum of the dorsal wall of 
the cesophagus. The cesophagus is very straight and narrow, 
slightly constricted at the septal regions, and does not change 
its character in any way until Segment xv. The walls through- 
out are much firmer and stronger, although no thicker, than the 
cesophageal walls in, for instance, Megascolex ceruleus. 
There is really more muscle present in them. 
When the other organs and the greater part of the septa are 
dissected away, it becomes clear that there is a segment of 
oesophagus belonging to each segment of the body, although, 
owing to the peculiar arrangement of Septum x and x1, the 
portion of cesophagus belonging to Segment x1 might be easily 
overlooked, as it is completely enclosed. In Segments xv, xv1, 
and xvi the cesophagus gradually dilates and its walls become 
a little thicker. In Segment xviit is the first of the series of 
gizzards. There are five gizzards belonging to as many succes- 
sive segments, i.e. the most anterior gizzard lies between Septa 
XVII-XVIII and xvi1I-xIx and the most posterior between Septa 
XXI-XX1I and xx1I-xx111 (fig. 22).! The gizzards differ very 
little from one another, that in Segment xviii is slightly 
smaller than the other four. The arrangement which obtains 
in each of these gizzard segments is as follows :—Immediately 
following the septum comes the gizzard itself; this is fairly 
globular in form, the greater part of its wall consisting of a 
ring of circularly-disposed muscle ; this ring of muscle is oval 
in longitudinal section, so that the lumen of the gizzard is 
smallest in the centre. Following the gizzard itself is a cylin- 
drical tubular portion of the cesophagus which joins that 
gizzard to the next following gizzard. Lastly, there are a 
1 It is especially necessary to insist upon this point, because Benham’s 
diagram (11), p. 295, would lead one to suspect a different arrangement. The 
gizzards should have been shown as they are in Perissogaster, Trigaster, 
or Hormogaster. : 
