Plate 8 



Xenopus tadpole tail epithelium. Near the end of the tail there are 

 only two layers of cells present and the mesodermal cavity has degener- 

 ated to the long gap A. No basement membrane lines the inner surfaces 

 of the cells in this site and at this time. Nil, nucleoleus ; N, nucleus ; m, 

 mitochondrion; L, phospholipid granule showing concentric whorls; 

 Mu, mucin pocket on the outer surface O of the cells; /, cytoplasmic 

 fibrils underlying the outer surface membrane. The inner surfaces of the 

 cells are poorly adhesive and pseudopods such as U project from the 

 unstabilized inner membrane ; at T the outer segment of the surface cells 

 is seen to be forming a close " adhesive contact " and incipient desmo- 

 somes D have appeared (see p. 90). 



