44 D. KEILIN 
(Mucihaematein or Thionin), which enable one to detect the 
most minute quantities of mucin. Moreover, to obtain a 
definite result by these methods, it was important to apply 
them simultaneously to the pharyngeal gland and to some other 
elandular cells which are known to contain mucin. The best 
control tissue of this kind is undoubtedly the external tegument 
of the same earthworm. In sections, not only of an extracted 
pharyngeal gland, but of the whole anterior portion of the 
earthworm, it is always possible to make a comparison of 
the staining reactions of the pharyngeal gland with those of the 
mucin cells of the skin. We willnow examine the longitudinal 
median sections of the anterior segments of Allolobo- 
phora chlorotica stained by the Mucihaematein method 
(see p. 88 of this paper). These sections, after thirty seconds to 
two minutes staining in 10 per cent. solution of Mucihaematein, 
show already a very clear picture of the distribution of mucin in 
the different tissues. These sections, when counterstained with 
Magenta-red and Picro-Indigo-carmine, become still more 
instructive ; the skin then shows clearly (Pl. 8, fig. 1), (1) the 
epidermal cells with greenish-yellow protoplasm and red nuclei, 
and (2) the mucin cells (mu. ¢.), in all stages of secretion of 
mucin, stained deep violet ; the small nuclei of these cells are 
displaced laterally or basally by the mucin (mu.), which in 
some cells is seen to issue from a small pore in the cuticle (cw.). 
The same sections show also the salivary secretion of the 
pharyngeal gland cells (Pl. 3, figs. 2 and 4, m. gl.). 
The basophile protoplasm of these cells is stained red, while 
the clear protoplasmic areas are now seen to be composed of 
sranular mass (mu.) stained, ike the mucin of the cutaneous 
sland, deep violet. This shows that the granular substance of 
the pharyngeal gland cells, which has been already mentioned 
by Stephenson, is composed of ordinary mucin. ‘The results 
obtained by the Mucihaematein method were corroborated 
by the Thionin method. Sections of the anterior portion of 
Allolobophora foetida prepared by this method have 
also shown the pharyngeal gland cells filled (PL. 3, fig. 9, m. gi.) 
with granules of mucin (mu.) similar to those of the mucin cells 
