PHARYNGHAL GLAND OF THE EARTHWORM 51 
could not trace any communication between thes cell aggregates 
and the pharyngeal or oesophageal walls, on account of the 
difficulty of following the course of these fine ductules in 
sections, I nevertheless believe that such communication 
exists. The function of these cells, as we shall see later, consists 
probably in elaborating a digestive enzyme which is discharged 
into the lumen of the pharynx or oesophagus. 
4. FUNCTION OF THE PHARYNGHAL GLAND CELLS. 
All the foregoing has proved, beyond doubt, that the pharyn- 
geal bulb of the earthworm is a true salivary gland, which 
pours its secretion (mucin) imto the lumen of the dorsal or 
salivary chamber of the pharynx. The mucinous salivary 
secretion accumulates in the pharyngeal cavity and oesophagus, 
and there it performs an important service during the operation 
of feeding. In view of the unusual diet of earthworms in general, 
it would be a matter of surprise to find that no special pro- 
vision was made by which the relatively enormous quantities of 
earthy matter, composed, in great part, of hard and insoluble 
particles, could be conveniently passed through the alimentary 
tract.’ 
In addition to the function of the formation of the food bolus, 
the salivary secretion has also a digestive function. In con- 
nexion with this digestive function of the pharyngeal bulb, it 
is interesting to examine briefly the available information con- 
cerning the digestive ferments of earthworms. 
Frédéricq (1878) was the first to discover in the alimentary 
canal of the earthworm the existence of two ferments: the one 
amylolytic, and the other proteolytic, the latter being active in 
either a slightly alkaline or a slightly acid medium. 
Darwin (1881, pp. 85-43), in his classical observations on the 
habits of earthworms, stated that they emit from the mouth an 
alkaline secretion, containing a ferment similar to the pancreatic 
1 In several earthworms, according to Vejdovsky and Eisen, the salivary 
portion of the pharyngeal wall is very easily protruded or evaginated from 
the buccal cavity and serves a more or less prehensile function, 
E 2 
