568 A. B. DAWSON 
granular or mucous cells. The granular cells never pass through 
a mucous stage before becoming completely differentiated. 
8. The granular secretion is elaborated within the cytoplasm, 
which is eventually completely transformed into secretion. The 
lumen is obliterated by the enormous increase in the size of the 
cells, whose walls later disintegrate, converting the body of the 
gland into a reservoir of secretion. 
9. The mucous secretion appears first as small vesicles in the 
cytoplasm. With the production of secretion the cells enlarge 
greatly and extend far into the lumen, and in many cases prac- 
tically fill it. The cell walls usually disappear in late stages. 
10. Giant nuclei are commonly found in developing granular 
glands, the largest observed being 260 u long, 10 » wide, and 6 u 
thick. 
11. Muscles of the granular glands are not developed till late. 
They are differentiated from the intercalary cells and are conse- 
quently of ectodermal origin. 
12. Mucus appears on the surface of the body in response to 
very slight stimuli. More violent stimuli induce proportionately 
larger discharges. 
13. Granular secretion is discharged only in response to very 
vigorous mechanical, chemical, or electrical stimulation. 
14. The mechanism of the discharge of mucus is unknown. 
Granular secretion is expelled from the gland by the contraction 
of investing musculature. 
15. Mixed glands, partly granular and partly mucous, are 
occasionally found. They represent stages in the displacement 
of the mucous epithelium by a new granular epithelium, which 
is differentiated from the intercalary cells. 
16. In the elaboration and expulsion of the secretion the granu- 
lar epithelium is usually destroyed. 
17. Regeneration is accomplished by the downgrowth of a new | 
epithelium which is derived from the intercalary region and the 
epidermis above. Leucocytes remove the remains of the old 
epithelium. The muscle layer is preserved intact. 
18. The manner of renewal of the mucous glands is not very 
apparent. The individual cells may function several times. 
