542 Franklin P. Johnson. 
is larger both in actual measurement and in proportion to the 
size of the vacuoles. In the lower part of the duodenum, these 
vacuoles are somewhat different from those found in the upper 
part and from those found in the cesophagus. Many of them have 
corresponding outbulgings of the epithelium on the mesenchymal 
surface. Some of these are constricted at their necks and form 
small side pockets, but for the most part they do not open into 
the main lumen of the duodenum. These ‘‘duodenal pockets,” 
if such they may be called, are presumably different from those 
referred to by Lewis and Thyng, which give rise to an occasional 
accessory pancreas. They differ also from the intestinal pock- 
ets in their position on the walls of the duodenum, their constric- 
tions are not always so well marked, and their cavities only occa- 
sionally open into the main lumen. However, so far as size and 
general appearance are concerned, they resemble the pockets of 
the jejunum and the ileum. Besides distinct pockets, all grada- 
tions between the simple vacuole of the interior and constricted 
side pockets are found in the walls of the duodenum. ‘These pock- 
ets of the duodenum, therefore, probably represent transition 
forms between the vacuoles of the upper part of the digestive 
tube and the intestinal pockets of the lower part. 
In the jejunum and the ileum at 19mm., there are 41 divertic- 
ula. These have the same general character as those of the 16 
mm. stage, but some, and especially those in the lower part of 
the ileum, are much larger. They are not equally distributed 
throughout the whole gut but are more numerous in the ileum. 
None are present in the upper part of the jejunum. 
In the duodenum of an embryo of 22.8 mm. the vacuoles are 
few above the opening of the ductus choledochus. Below this 
level, fig. 16, they are numerous and larger in proportion to the 
size of the tube than at 19 mm. Moreover, they do not form du- 
odenal pockets as in the 19 mm. stage. They cause the whole 
lumen to be broken up, and, as shown by modelling, the lumen 
in this region is occluded. This stage, therefore, as far as the vac- 
uoles are concerned, resembles the condition found at 16 mm. 
more than that found at 19mm. In the jejunum and ileum 33 
pockets were counted. Again they vary in size, the largest meas- 
