492 W. R. Coe — Anatomy of Cerebratulus lacteus. 



its free border and has its opposite end continued into a slender, 

 often branched, fibre-like process. The nucleus (w) is placed in the 

 lower part of the upper, broadened portion of the cell. These cells 

 are regularly arranged with all their oval nuclei at about the same 

 level. Glandular cells are scattered among the ciliated cells.* 

 Beneath the superficial layer are elongated clusters of gland-cells 

 closely packed together. Each cluster of cells apparently has a 

 single duct leading through the ciliated layer to the lumen of the 

 oesophagus. The individual gland-cells are large, oval or elongated, 

 and contain a small nucleus pressed to one side of the mass of deeply- 

 stained secretion, similar to that often found in the duct. 



The intestine comprises much the largest portion of the alimentary 

 canal, and to further increase its surface there are broad, paired 

 diverticula of the main canal throughout its course. These intes- 

 tinal cseca are often forked or lobulated distally, especially above and 

 below the median horizontal plane (Plate XIV, fig. 10). The main 

 canal (i) is comparatively small, and in transverse sections appears 

 somewhat flattened and broadened above, while the narrow ventral 

 border lies near the ventral wall of the body (Plate XI, fig. 4). 



The intestine lacks muscles almost entirely, the caeca being directly 

 surrounded only by connective tissue, and although there is a double 

 set of dorso-ventral muscles reaching between each pair of caeca 

 nearly to the main canal, these belong rather to the body-muscula- 

 ture than to the intestine. The epithelium consists of long, columnar 

 cells (Plate XIII, fig. 2) which are prolonged below into slender, 

 often branched, processes. Many of the cells are ciliated, but those 

 cells which are most characteristic of this portion of the alimentary 

 canal are more or less completely filled with colorless, refractive 

 granules (s) resembling globules of oil or fat. It often happens that 

 in mounted sections these granules stain intensely and resemble 

 minute nuclei. The nuclei {n) of the cells are usually placed just 

 above the filiform processes {iid). The granules occur most abund- 

 antly above the nucleus, although they are sometimes found beneath 



it.t 



At the posterior end of the intestine the caeca become very small 

 and shallow, and disappear entirely in the short rectum which lies 



* In Carinella the arrangement and structure of these ciUated and glandular cells 

 (Plate XIII, fig. 4) are easily made out. 



f In Micrura affinis (Plate XIII, fig. 3) these long, slender cells are arranged with 

 great regularity about the intestinal lumen, and have conspicuous cell-walls, which is 

 not the case in any sections of C. lacteus which I could obtain. 



