1 8 Journal of Comparative Neurology. 



mis, each organ is not only surrounded by the bodies of the 

 epidermal cells, but among these are many gland cells which 

 when distended by their secretion, crowd the structures around 

 them. Thus the cells of the sense-organs in this region must 

 be crowded into a small space. In the cirri, the region in 

 which the sensory cells lie — i. e., the region between the bodies 

 of the epidermal cells and the axial nerve — is filled merely by 

 fibrous connective tissue. The sensory cells in this region, 

 therefore, are less crowded and are generally more elongated — 

 varying from 4 to 12 ju in length and from i to 4 /< in width. 



Each group of cells has its long axis oblique to the longi- 

 tudinal axis of the cirrus and the peripheral processes — i. e. , 

 the peripheral nerve-fibers — from a given group pass together 

 for a short distance in a course which is oblique to the bodies 

 of the epidermal cells. If the group of cells belongs to a single 

 organ, all the peripheral processes take the same course between 

 these cell bodies. If the group belongs to two or more organs, 

 the bundle of peripheral processes soon separates into two or 

 more smaller bundles which diverge from each other ; each 

 smaller bundle then takes its separate course oblique to the bod- 

 ies of the epidermal cells. 



As a given bundle of peripheral processes passes between 

 the bodies of the epidermal cells, it generally becomes slightly 

 less in diameter and bends so that its course is almost at right 

 angles to the cuticula. Quite often, however, the bundle of 

 fibers continues its oblique course until almost to the cuticula, 

 then turns and passes at right angles to it. The peripheral ends 

 of the epidermal cells are thickly covered with brown pigment 

 which does not quite reach the cuticula. In sections the posi- 

 tion of the bundle of peripheral processes among the epidermal 

 cells is clearly indicated by the absence of pigment among these 

 processes, so that, wherever such a bundle approaches the cuti- 

 cula, the band of brown pigment is interrupted by a clear area. 

 It is these clear areas which first catch the eye and enable one 

 to locate the peripheral ends of the sense-organs. 



As a bundle of peripheral processes approaches the cuti- 

 cula, the individual processes separate from one another (Plate 



