FIG. 3. The basal portion of a mucous neck cell from a gastric gland of the bat. 

 The nucleus at the lower right contains the nucleolus (nu) and is limited by the 

 prominent nuclear envelope (ne) . A mucous granule is shown at mg and mito- 

 chondria at m. The cytoplasm of this cell is characterized by a prominent develop- 

 ment of the rough form of the ER, (rer). The individual elements in the section 

 appear as slender line-limited profiles representing sections through lamellar cis- 

 ternae. The surfaces of these membranes facing the matrix of the cytoplasm are 

 densely coated with ribosomes. This micrograph serves to illustrate a variant of the 

 ER which is common in cells dedicated to the single task of protein synthesis. The 

 total membrane surface for the support of ribosomes is large and the space within 

 the system for the sequestration of the synthesized material is correspondingly 

 extensive. Magnification: 30,000 X. 



128 



