326 The Alligator and Its Allies 



(sc) is here differentiated into three areas — a 

 dense, deeply stained area immediately around 

 the neurocoel ; a less dense area of cells surrounding 

 the inner area and extending ventralward as a 

 rounded projection on each side; and an outer 

 layer, with few or on nuclei, surrounding the inner 

 two layers except on the dorsal side. 



In Figure 2oi the size and complexity of the 

 figure are due, it will be easily understood, to the 

 fact that the plane of the section passed through 

 the curve of the body, thus practically cutting 

 the embryo in two regions — an anterior, where the 

 lungs (III) and liver (li) are seen, and a posterior, 

 where the Wolffian bodies (wt) are present. The 

 spinal cord and the surrounding structures have 

 almost the same characteristics at both ends of the 

 figure, except that the primitive spinal column is 

 rather more distinct in the posterior end of the 

 section. The posterior cardinal veins (pc), Wolf- 

 fian ducts (wd), and Wolffian bodies {wt) are also 

 prominent structures of this end of the figure, 

 the last being made up of a great number of tubules. 

 The extreme anterior ends of the Wolffian bodies 

 are seen in the other half of the section in the upper 

 angles of the body cavity, dorsal to the lung rudi- 

 ments (lu). Filling most of the body cavity (be) 

 and making up the greater part of the middle of the 

 figure are the liver (li) , now a very large organ ; the 

 stomach {i'), also quite large; the pancreas (pafi), a 

 small body lying near the stomach; and the lungs 



