coe: nemerteans of west and noethwest coasts. 131 



bluish with haematoxylin -orange, while the other cells {gl) are 

 thickly packed with minute vacuoles of secretion which take the 

 orange stain with the same comV)ination. 



Beneath the epithelium is a thin layer of connective tissue in 

 which the two large proboscis nerves are imbedded, and beneath 

 this a thin layer of circular muscles. Next toward the periphery 

 comes the thick layer of circular muscles, of very coarse fibers, and 

 of several times the thickness of the circular layer. Outside the 

 longitudinal muscles lies a la^^er of homogeneous, but tough and 

 firm, connective tissue (bm) which shows no indication of fibers. 

 This is a sort of basement layer, usually more than half as thick as 

 both muscular layers, and is especially characteristic of the anterior 

 chamber. I know of no other species of nemertean where this layer 

 is so well developed. It gradually disappears at the posterior end of 

 the anterior chamber, but reappears internal to the longitudinal 

 muscle of the middle chamber. Outside the basement layer is the 

 usual thin layer of flattened epitheUum bathed in the fluid of the 

 rhynchocoel. 



At the posterior end of the anterior chamber the proboscis dimin- 

 ishes greatly in diameter, its lumen becoming reduced to a narrow 

 canal which lies excentrically, but the circular muscles (PI. 11, fig. 

 69) become enormously increased. This canal is much twisted, and 

 after a short distance opens into the middle chamber, with its wide 

 lumen and very peculiar epithelial lining. The exact nature of this 

 epithelium is very difficult to determine. The cells are columnar 

 (PI. 11, fig. 66 2^^1^)^ with homogeneous cytoplasm, and their oval 

 nuclei arranged for the most part in two layers. One of these is 

 situated near the base of tlie cells and the other well up toward the 

 free border. Both the cells and their nuclei are very much smaller 

 than those in the anterior chamber. Between the borders of the 

 cells and the actual lumen of the proboscis are two layers of a some- 

 what uncertain nature. Apparently each columnar cell (PI. 11, fig. 

 66) bears a single well-developed flagellum {fl), which is perhaps 

 three fourths as long as the cell, and which seems to end distally in 

 a thick mass of opaque, granular secretion [s). This secretion forms 

 a thick layer around the actual lumen of the proboscis. The two 

 nerves lie in the basal portion of the epithelial layer (PI. 11, figs. 

 66, 71). The present evidence seems to indicate that this middle 

 chamber represents a highly specialized, sensory portion of the pro 



