Vol. 3] Torrey. — Biological Studies on CorymorpJta. 287 



Fig. 30. The striking feature of it is the differentiation of the 

 endodermal epithelinm. There are four regions in which the 

 epithelium is normal or approximately so, and four intervening 

 regions in which certain cells have increased enormously in bulk 

 and met across the enteric cavity, dividing it into four parts 

 (A-D). These openings vary in area. Two of them (C and D) 

 are much larger than the others and show signs of further divi- 

 sion that demonstrate the method by which the original four 

 openings were formed. The epithelium bounding C and D on 



Fig. 32. Transverse section of young stem, showing formation of canals 

 (A, B, C, D) and axial parenchyma. X 280. 



the outside is divided in each case into two lateral groups of 

 normal cells and a median group of two or three cells which 

 have begun to absorb water and bulge out into the canal. These 

 median groups represent the beginnings of more partitions like 

 those which separate A and C from B and D. One of the cells 

 in each will swell until it reaches and fuses with the vacuolated 

 cells which have already united in the center. Other divisions 



