MUCOUS MEMBRANES AND GLANDS. ^3 



the primary arrangement of the gland is modified by subsequent 

 changes to such a degree that the original plan of its structure is 

 recognized with difficulty. The sexual glands are so highly special- 

 ized that in their development they deviate materially from the mode 

 of the formation of the typical secretory organs. Ordinarily the 

 elaborating glandular cells are ectodermic and entodermic in origin, 

 while the basement-membranes and supporting tissues are meso- 

 dermic. 



