20 Journal of Comparative Neurology. 



Fig. 3 and Plate II, Fig. 36). The living nerve-cells have a 

 rather coarsely granular central protoplasm surrounded by a 

 clear outer neuroplasm. The same parts may be seen in both 

 central and peripheral processes, each of which has a granular 

 axial strand and a clear outer neuroplasm. The sensory hair 

 itself contains no trace of the granular axial part but appears to 

 be composed entirely of somewhat rigid neuroplasm ; or it may 

 be that the extreme peripheral end of each sensory cell, like 

 that of each of the epidermal supporting cells, is actually cuti- 

 cularized. That the sensory hair is not attached to the general 

 cuticula but is a prolongation of the peripheral process itself is 

 shown by the fact that, whenever a contraction of a peripheral 

 process takes place, the sensory hair is always drawn partly or 

 wholly beneath the cuticula (Plate I, Fig. 4). In the methylene 

 blue preparations, the peripheral processes are often varicose ; 

 a large swelling may form at a point where one peripheral pro- 

 cess branches (Plate II, Fig. 35) or the sensory hair itself may 

 be swollen into a ball which lies on the external surface of the 

 cuticula (Plate I, Fig. 4). This may even happen to all the 

 sensory hairs in one group and then the entire group appears 

 above the cuticula as a crowded group of spherical bodies (Plate 

 I, Fig. 20). It must be born in mind, however, that these 

 varicosities and swellings are all artefacts. 



The central processes from the cells of the diffuse sense- 

 organs present exactly the same appearance as the peripheral 

 ones. The central fibers from one group of cells pass, either 

 alone or after joining those from other groups, to the longitudi- 

 nal axis of the cirrus and enter the axial nerve (Plate I, Fig. i). 

 The center of this nerve contains the central processes or nerve 

 fibers from organs lying in the tip of the cirrus; passing toward 

 the base, each organ adds its fibers to the outer surface of the 

 nerve in its neighborhood, and the outermost fibers of the nerve 

 at its base thus come from the organs lying in the base of the 

 cirrus. Generally the fibers enter the axial nerve on the side 

 on which their cells lie, but occasionally they cross the axial 

 nerve and enter it on the opposite side. 



