PLATE XVII. Fig. 29. The gland cells of the ectoderm of the pedal disk. 

 There is no cuticular substance on the surface (S). Small cytoplasmic proc- 

 esses extend from the surface of the cells. The granules (G) are probably the 

 secretion manufactured by these cells, especially those with more double 

 membranes and fev/er and smaller granules farther from the surface, to 

 cement Hydra to the substratum. 



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