NOTES ON THE STRUCTURE OF OIKOPLEURA. 43 
and 8). Inside the ectoderm on this dorsal aspect a very 
thin layer of connective tissue (parietal mesoderm) can 
now be recognised (fig. 8, mes). 
We now come upon the posterior end of the stomach. 
This organ is of large size and complicated shape, it 
extends from about the 50th to the 160th section. There 
are two great laterally placed posterior lobes which join 
anteriorly. Into one of these lobes, the left, the oesophagus 
opens, while the intestine emerges from the other, on the 
right side. They may be conveniently referred to as the 
cardiac (left) and the pyloric (right) sacs respectively. 
These lateral posterior parts of the stomach are of con- 
siderable dorso-ventral extent (see Pl. Il. fig. l, s?, s¢’), 
while the anterior or median part of the stomach where 
the cardiac and pyloric sacs join is low, but very wide from 
side to side (Pl. II. fig. 5). The greater part of the 
alimentary canal is richly ciliated (Pl. I. fig. 10). I have, 
however, not been able to find any trace of cilia in the 
cardiac sac which 1s very much more glandular, especially 
in its ventral end (PI. II. fig. 1, gl) than any other part of 
the stomach. 
The pyloric sac extends a little further posteriorly than 
the rest of the stomach, and is seen in fig 7, Pl. I. with 
the flattened diverticulum from the oesophagus lying 
dorsally. In the next figure (Pl. I. fig. 9), which shows 
the 6lst section, the cardiac sac is just beginning to 
appear below the cesophagus, and ten sections further 
forward (Pl. I. fig. 10) the two are found to communicate, 
the cesophagus having turned ventrally with a shght un- 
dulation. The pyloric sac is now large and lies with its 
long axis dorso-ventrally. Its imterior, and that of the 
cesophagus, 1s ciliated while the cardiac sac shows glandu- 
lar cells at its ventral end (Pl. I. fig. 10, gl.). 
The last three figures show the gradual reduction in 
