arynx, _ph_, as seen in the figure, is
smaller than it is in reality because of the small dorso-ventral
diameter (the only one here shown) compared to the lateral diameter. The
end of the lung rudiment, _lu_, is slightly enlarged and lies in a plane
nearer to the observer than that of the oesophagus, _oe_, though this is
not well shown in the figure.

The oesophagus, _oe_, diminishes slightly in caliber for a short
distance caudad to the origin of the lungs, then gradually increases in
caliber until it suddenly bends to the side (towards the observer) and
merges into the wide stomach, _i'_. The stomach, which is irregularly
conical in shape, lies in a place slightly nearer the observer than the
end of the lung rudiment mentioned above.

Lying to one side of the stomach and duodenum, and extending cephalad
beyond the end of the lung rudiment is the liver, _li_, whose outline is
only roughly shown here by the broken line. The stomach opens rather
abruptly into the duodenum, _d_, which slopes back towards the plane of
the oesophagus (away from the observer).

The projection from the side of the duodenum, _pan_, not well figured
here, indicates the position of the pancreas, better shown in the next
reconstruction. The duodenum extends only a short distance caudad to
this point and then opens, _aip_, to the yolk-sac.

The yolk-stalk, or unclosed region of the enteron, is still of
considerable extent, though its exact boundaries are not easy to
determine. The distance between the anterior and posterior intestinal
portals is approximately shown in the figure under discussion.

The hindgut is cylindrical in cross section and of about the same
diameter throughout, except for a slight enlargement in the cloacal
region.

The post-anal gut is not shown here; it will be described in connection
with the next reconstruction where it is figured.

Figure 6 is a surface view in profile of an embryo of the next stage to
be studied. The manus and pes are here well developed, and the general
development of the embryo is in considerable advancement over the last
stage studied.

Figure 6A represents a reconstruction, from a series of transverse
sections, of the enteron of an embryo of about the age of the one shown
in figure 6. The outlines of the entire embryo, of the eye, _e_, and of
the anterior, _aa_, and posterior, _pa_, appendages are shown by broken
lines. Its position being coincident with that of the stomach, liver,
and pan