DOUYMEXIA ACUTA. 99 



figs. 1, 7). Numerous muscles inserted in the tissue of the fold and on the other 

 hand to the body wall doubtless serve to dilate the canal when the animal is 

 in the act of feeding. Inunediately behind this fold, and therefore in the region 

 of the radula, the canal becomes much wider but more posteriorly again narrows 

 and by a comparatively small opening connnunicates with the stomach-intestine. 

 Throughout the entire extent of the ])iKuynx its epithelial lining is tludwn into 

 numerous longitudinal folds, especially in the neighborhood of the raduhi whoie 

 they become wavy and in sections present a most complicated appearance. In 

 general the cells of the pharyngeal epithelium are low columnar elements dcNuid 

 of cilia and overlaid with a clearly defined euticular layer. 



Two sets of salivary glands are present, a ventral pair and a group of cells 

 imbedded in the large fold just mentioned. The cells of the last named gland, 

 which is probably the homologue of the dorsal salivary gland of several other 

 species of Solenogastres, are not grouped compactly as in P. hawaiiensis, for 

 example, but are scattered throughout the tissue of the fold and ojien by separate 

 pores over its entire extent. All the cells are i)yriform and in early stages are 

 composed of a finely vacuolated cytoplasm in which the secretion ultimately 

 makes its appearance in the form of distinct granules of comparatively large 

 size. These rarely accumulate to a sufficient extent to hide the nucleus but make 

 their way bj^ well-defined ducts to open by intercellular channels into the pharyn- 

 geal cavity. 



The ventral salivary glands open into the pharynx at the sides of the extreme 

 tip of the radula, and in the form of tubular outgrowths extend backward for a 

 distance of 3.5 mm. As may be seen (Plate 15, fig. 2), the ducts are of large size 

 and are bounded by slender cells densely filled with a secretion having nnich tlu> 

 same appearance as that developed in the dorsal set. 



The radula is of the polystichous type, and judging wholly from sections 

 consists of 48-51 rows with twenty-two teeth in each row. All the teeth are 

 of essentially the same shape (Plate 34, figs. 7, 11) and size with the exception 

 of those on each side of the mid line which appear to be slightly smaller. A 

 very thin yet clearly defined basement nicnibiane is i^resent. 



The radula sac rests upon a support consisting of a series of globular cells 

 of which two are of relatively large size and are located synunetrically on each 

 side of the mid line. All of these contain nuclei and a finely granular cytoplasm, 

 which in the larger cells is usually greatly slu-unken. To these supports numer- 

 ous muscles attach, but from sections it is most difficult to describe their relations 

 and define their function. 



