304 The Alligator and Its Allies 
body cavity (bc). The pleural sides of these 
crescentic portions of the body (or pleural) cavity 
—that is, the boundary of the mass of mesoblast 
just mentioned—are lined with a thickened layer of 
cells, shown by the solid black lines in the figure. 
The lung rudiments may be traced through about 
fifty sections of this series, or about one twelfth of 
the entire series. At the dorsal angle of the part of 
the body cavity (bc) just described, near the dorsal 
aorta (ao), are two dark, granular masses (ge), 
which, under a higher magnification than is here 
used, are seen to consist of a small group of blood- 
vessels filled with corpuscles; although several 
sections in front of the anterior limits of the kid- 
neys these are evidently glomeruli. They may 
be traced, though diminishing in size, far toward 
the tail, in close connection with the Wolffian 
bodies. At intervals they are connected by nar- 
row channels with the dorsal aorta; no such con- 
nection was present in the section drawn. The 
notochord (n#), spinal cord (sc), muscle plates (mp), 
and spinal ganglia (sg) need no special mention. 
The mesoblast is beginning to condense in the 
neighborhood of the notochord, and the ectoderm 
is slightly thickened laterally and dorsally. 
Figure 16e is in the region of the liver and the 
Wolffian bodies; it also shows the tip of the ven- 
tricular end of the heart. The liver (iz) is a large 
irregular mass, of a blotchy appearance under this 
magnification, lying between the heart (vm) and 
