84 PRONEOMENIA HAWAIIENSIS. 



bands of cells situated a short distance within the body on each side of the ventral 

 furrow into which their secretion is poured. In the body proper the position, 

 size, and number of the component cells in cross section is shown (Plate 14, fig. 3). 

 This condition of affairs exists to the front end of the gonad where the gland cells 

 become more abundant and of larger size, occupying approximately one fourth 

 of the visceral cavity at the level of the posterior end of the radula. Their 

 outlets still continue in the ventral furrow and in addition occur throughout 

 the region of the anterior division of the foot, which contams extensive blood 

 lacunae and may probably be protruded at times beyond the ventral furrow. 



The anterior pedal gland abuts against the front end of the pedal gland 

 proper and, occupying more than half of the space between the buccal mass 

 and the body wall, extends as far forward as the brain. The main body of each 

 of its cells consists of spongy cytoplasm containing an abundant secretion that 

 stains faintly in Delafield's haematoxylin. The included nucleus is relatively 

 very small, granular and very irregular in form. Several cells are usually grouped 

 together and surrounded by a few connective-tissue fibres. Each cell is attached 

 by a duct with the ventral furrow chiefly in front of the foot. All of the ductules 

 of both pedal glands open between the cells of the ventral furrow. 



The atrial opening leads into a cavity of relatively generous proportions 

 (Plate 5, fig. 2) with walls abundantly supplied with sense organs of several 

 different types. The most external of these, which I have termed the outer 

 atrial ridge (Plate 14, fig. 1), presents the appearance of a low prominence situ- 

 ated just within the lips and encircling the atrium except in the mid line behind. 

 Its cells are comparatively slender and in addition to the darkly staining and 

 usually basally situated nuclei, they contain numbers of greenish yellow pig- 

 ment granules. Lying in contact with the inner ends of these cells is an accumu- 

 lation of ganglion cells forming an elongated mass coextensive with the ridge 

 itself. From it nerve fibres may readily be traced to the sensory cells adjoining, 

 and in an opposite direction large nerves occasionally pass inward, and soon be- 

 come confused with the ganglionic elements attached to the bases of the cirri 

 above. That this is a highly sensory structure there is no reasonable doubt, 

 but to define its function more accurately is at present impossible. 



Of almost identically the same length as the sensory ridge just described and 

 directly in contact with its inner border is another inwardly projecting fold 

 of much greater height and widely different character. It likewise encircles 

 the atrium save on the posterior side where its free extremities unite with another 

 ridge of corresponding height and appearance that farther within the body also 



