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THE MESODERMAL DERIVATIVES 



The Adrenal Cortex (Interrenal Gland). The cortical cells 

 of the adrenal gland may be seen as early as the 10 mm. body length 

 stage, and probably arise from the coelomic mesothelium. They are 

 aggregated into round or elliptical bodies lying on the dorsal surface 

 of the coelomic cavity, just ventral to the dorsal aorta. The original 

 mass measures about 0.8 mm. in length. It contains a number of 

 nuclei embedded in a syncytial mass of acidophilic tissue. The con- 

 tained granules may be pink, yellow, or black. By the 12 mm. stage 



Cortical cells 



Adrenal gland of the recently metamorphosed frog. Camera 

 lucida drawing illustrating the detailed nature of an islet from 

 the interrenal region. (From Stenger and Charipper: 1946.) 



paired gonad primordia may be seen, also in the dorsal coelomic 

 epithelium but in a more lateral position. By the 13 mm. stage the 

 cortical masses have doubled. They form a cap around the base of 

 the upper four-fifths on either side of the dorsal aorta, just posterior 

 to the site of formation of a single aorta. At this stage the cortical ma- 

 terial may be seen intermingled with, or in close proximity to, the 

 gonad anlage. 



By the 37 mm. body length stage the adrenal cortex consists of 

 lobed masses of cells surrounded by the notochord, the body wall, 

 and the Wolffian duct below. Groups of cortical cells are, by this 

 time, encapsulated and come into intimate association with the mes- 



