On the Pharyngeal or Salivary Gland of the Earthworm.

Abstract

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 lying in the conductive musculo-vascular portion 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 epithelium 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 bacteroid or uric acid cells and amoebocytes, similar to the yellow cells of the alimentary canal.