12 WALTER K. FISHER, 



about the visceral loop. That of the left side is a trifle more elongate 

 and has a similar position, being wedged in between the septum of 

 the head cavity and the gonad, and posteriorly between the gonad 

 and oesophagus. It is all but impossible to differentiate this from the 

 wall of the oesophagus in a preserved specimen. If the septum of 

 the head cavity on the right side be removed, however, and stained 

 with haematoxylin, cleared and mounted, the gland is seen to consist 

 of many tiny lobules, which, uniting, form larger ones, till a racemose 

 structure is the result. Out of this, several collecting tubes unite 

 into one, which passes forward beside the pharynx, as described above. 

 Under the microscope the duct is seen to consist of a central cavity 

 lined by small cubical cells, rather indistinct. Either in the lumen or 

 to one side a small nerve (arising from the stomatogastric ganglia) 

 passes along the whole length of the duct. Crowded about the small 

 cells lining the lumen are large cells of two sorts : lesser pear-shaped 

 cells full of heavily stained granules, and greater, more numerous, 

 much vacuolated ones (Fig. 12). The gland itself is simply a repetition 

 of this structure, save that the small lining cells are absent except 

 in the collecting tubes. In many of the lobules there seems to be 

 little or no lumen. In a whole-mount of the gland the granular cells 

 stain heavily and can be readily detected. They are outnumbered by 

 the larger vacuolated kind. I am unaware of the nature of the 

 secretion. 



The posterior, salivary, or pharyngeal glands (Figs. 1, 3 etc. Ph. G) 

 are conspicuous, being tufted structures on either side of the pharyngeal 

 dilation. They are composed of groups of small finger-like blind tubes 

 opening into tiny pockets, which, in turn are divisions of the lateral 

 sacculations of the pharynx (Fig. 8). Rarely these acini or ultimate 

 glandules are branched once, and the tips, in preserved specimens at 

 least, are likely to be slightly swollen. In fresh specimens the acini 

 are very long, reaching, if turned back, quite across the pharynx. 

 The epithelium lining the tubules is low, the cells possessing small 

 deeply staining nuclei. In the distal part of the tubule the lumen is 

 filled with loose tissue, apparently proliferated from the epithelium, 

 which seems to store the secretion, for when empty only cell walls 

 are seen. The secretion stains deeply and is found in the distal end 

 of the glandule. In Acmaea patina this gland is relatively much 

 smaller, the acini being larger and scattered, not in little bunches or 

 tufts. Similarly the anterior or buccal gland is larger and the com- 

 ponent parts more conspicuous. Otherwise they seem much alike in 



