No. I.] SENSE-ORGANS OF LUMBRICUS AGRICOLA. 199 



are from 35 to 45 in one of the larger sense-organs. These 

 sense-cells stain about the same color as the supporting cells, 

 but appear more finely granular and differ from them greatly 

 in form. I have found no intermediate forms between the 

 sense-cells and the supporting cells. The supporting cells are 

 either of the same width throughout their height, or slightly 

 wider at base and apex; they have clearly defined cell-walls, 

 and the walls of one cell are closely applied to those of sur- 

 rounding cells; on account of mutual pressure the outline of 

 a cross section of a cell is nearly hexagonal. The sense-cells, 

 on the other hand, are much narrower at base and apex; in 

 the upper part of each cell it is impossible to distinguish any 

 cell-wall, and it is difficult to see one in the lower part ; each 

 cell stands alone, clearly separated from its fellows by a space 

 which appears as if filled by a fluid, and a cross section of 

 a cell is circular or elliptical instead of hexagonal. In a longi- 

 tudinal section through the center of a sense-organ one might 

 at first suppose these cells had been torn apart in the prepara- 

 tion. 



The greater part of the sense-cells have their nucleus at or 

 below the middle of their height; a few cells, usually situated 

 between the center and the lateral surface of the sense-organ, 

 have their nucleus near the cuticula. The part of the sense- 

 cell in which the nucleus lies is always the widest part, and 

 is almost completely filled by the nucleus. If the nucleus 

 occurs near the cuticula, the cell tapers into a very slender, fibre- 

 like base. If the nucleus is found at the middle height of the 

 cell or near the base, the base of the cell does not become so 

 slender, and often sends off several basal processes which pass 

 to the basement-membrane between the small basal cells. 

 Above its nucleus, each sense-cell tapers into a slender part 

 which looks like a delicate strand of protoplasm and reaches 

 to the cuticula. Each cell terminates in a still more slender, 

 hair-like process which passes through a canal in the cuticula 

 and projects stififly for about 2/x above the surface. The 

 varying position of the nuclei in the sense-cells seems unim- 

 portant, and is probably brought about by the cells accommo- 

 dating themselves to the space in which they lie. The nuclei 



