PHARYNGEAL GLAND OF THE EARTHWORM 53 
roborated by the fact that the extracts from the oesophageal 
portion, which, as we have seen, is surrounded only by the 
non-mucinous glandular cells, contains, according to Willem 
and Minne, a proteolytic ferment, although in smaller quantity 
than that of the pharyngeal bulb. 
Having established the glandular nature of the pharyngeal 
bulb, and having shown its function, it seems to me quite 
superfluous to seek further proof in a study of the development 
of the pharyngeal glandular cells. As to the origin of these 
cells, Stephenson’s statement that they are derived from the 
peritoneal layer appears to me to be doubtful. His descrip- 
tion, and especially his figures, do not give the slightest support 
to this opinion, and I consider that the question of the develop- 
ment of the pharyngeal gland cells remains still open for 
further investigations, 
5. SUMMARY AND CONCLUSIONS. 
1. The pharyngeal dorsal bulb of the earthworm is a true 
salivary gland. 
2. The function of the basophile cell-aggregates of this bulb 
is the production of mucin and a proteolytic enzyme. 
3. These products of secretion are collected in a system of 
salivary ducts lymg in the conductive musculo-vascular por- 
tion of the pharyngeal bulb. The salivary ducts, on reaching 
the pharyngeal ciliated epithelium, divide into innumerable 
fine ductules which penetrate between the epithelial cells and 
terminate near the free surface in the discharge pockets. The 
salivary secretion accumulates in these pockets before it is 
discharged into the dorsal or salivary chamber of the pharynx. 
4. The club-shaped fibrillae of the pharyngeal epitheliam 
discovered by Retzius are not of a nervous nature, as he 
supposed ; they are the ordinary salivary ductules with their 
discharge pockets. 
5. The question as to the development of the pharyngeal 
bulb of the earthworms remains open for further investigations. 
6. In addition to the glandular cells with their ducts, muscles, 
nerve fibres, and blood-vessels, the pharyngeal bulb contains 
