362 W. S. NICKERSON. [Vol. XVII. 



longitudinally downward. The interior of these cells becomes 

 hollowed out to form elongated tubules and the cytoplasm 

 metamorphosed into the bodies described, the process agree- 

 ing closely with that described by Davenport ('93), p. 7, in the 

 formation of the yolk granules of Urnatella. 



In fully mature animals the interior of the stalk appears to 

 be filled in some cases by a gelatinous mass almost destitute 

 of structure, and the rounded cytoplasmic bodies are scattered 

 through every part of the parenchyma. 



Digestive System. — The digestive system in L. Davenporti 

 is similar to that described for other members of the genus 

 (PI. XXXII, Fig. 7). It consists of a t/'-shaped tube having its 

 oral end just inside the anterior margin of the lophophore and 

 opening at the anal end upon a small elevation or papilla rising 

 from the center of the lophophore into the cavity of the atrium. 

 Its wall is composed of a single layer of epithelial cells which 

 bear long, thickly set cilia, except those forming the glandular 

 portions of the wall of the stomach. The descending limb of 

 the U is formed by the oesophagus or gullet, which is over- 

 hung at its oral end by the epistome, a fold of the vestibular 

 epithelium ciliated upon its oral face (PI. XXXII, Figs. 5 and 7). 

 At its lower end it is slightly narrowed and bends sharply inward 

 to open into the basal portion of the stomach. 



The stomach, which is formed by a considerable enlargement 

 of the digestive tube, has its long diameter nearly parallel with 

 the long axis of the body. The cilia are here shorter than in 

 other regions, and are entirely absent from the portions which 

 are of a distinctly glandular nature. These regions are three 

 in number, two of which occur as a pair of thickened ridges 

 near the basal end of the organ, one on either side of the 

 opening of the oesophagus (PI. XXXII, Fig. 4 ; PI. XXXIII, 

 Fig. 24). In the living animal they appear whitish and opaque. 

 The cells forming these thickenings are long, narrow, and filled 

 with fine granules which stain deeply with iron-haematoxylin, 

 giving to the cells of this region a dark, slaty-blue color. The 

 nuclei are basal in position. A few small vacuoles are sometimes 

 present, while at the free ends of the cells, occupying a narrow 

 strip next to the lumen, there is often a zone of small spherical 



