304 The Alligator and Its Allies 



body cavity (be). 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 (be) 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 glomeriili. 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 (nt), 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 i6e 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 (It) is a large 

 irregular mass, of a blotchy appearance under this 

 magnification, lying between the heart {v7i) and 



