The Development of the Alligator 331 
gated cavity whose ventral wall is in close contact 
with a group of small, darkly staining alveoli (p), 
the pituitary body. Extending posteriorly from 
the pituitary body is a gradually thickening mass of 
cartilage (bp), which surrounds the anterior end 
of the notochord (z#) and may be called the basilar 
plate. Inits anterior region, where the section is 
nearly median, the spinal column shows its canal, 
with the enclosed spinal cord, while toward the 
posterior end of the figure the vertebre are cut to 
one side of the middle line, and hence show the 
neural arches (ma) with the alternating spinal 
ganglia (sg). Near the posterior end of the figure 
the pelvic girdle (pl) is seen. The largest organ of 
the embryo, as seen in this section, is the heart, of 
which the ventricle (vm) seems to be closely sur- 
rounded, both in front and behind, by the auricles 
(au). The liver (Jz) is the large, reticular mass 
back of the heart. Dorsal and anterior to the 
liver is the lung (Ju), now of considerable size and 
development. The enteron is cut in several places 
(oe, 7) and its walls are beginning to show some 
differentiation, though this cannot be seen under 
the magnification here used. One of the Wolffian 
bodies is seen as a huge mass of tubules (wt) extend- 
ing from the pelvic region, where the mass is 
greatest, to the region of the lungs. The Wolf- 
fiian tubules stain darkly and the whole structure 
forms a very striking feature of the section. Dor- 
sal to the posterior end of the Wolffian body is a 
