384 MARGARET LEWIS NICKERSON. [Vol. XVII. 



of the microscope, by the presence of a bulb-like structure pro- 

 jecting above the general surface of the cuticula. It is this 

 bulb which constitutes the distinction between the first and 

 second types of epidermal bodies. In other respects there is 

 much similarity, and the two types are perhaps to be regarded 

 as fundamentally the same. A comparison of the two types 

 might suggest that the bulb is a temporary structure produced 

 by the effect of reagents or by a violent muscular contraction ; 

 but examination of a large number of sections from specimens 

 preserved in different ways showed that no matter what the 

 method of killing, organs exhibiting these bulb-like protuber- 

 ances were always present, even when the cuticula had been 

 removed before placing the tissue in the fixing fluid. Again, 

 pieces of the body wall cut from living worms and examined 

 under the microscope showed the presence of these bulbs. 



The organs of this type first appear on the introvert some- 

 what anterior to the nephridial openings. Here they are very 

 rare. They increase in number, however, backward, until in the 

 region of the nephridia they are so numerous that several are 

 found in one transverse section. In the tail region they are even 

 more abundant. Occasionally there may be found in a section 

 two successive organs belonging to the same type, but far more 

 often they are separated by a considerable distance. They are 

 found at intervals in all parts of the body of the worm except the 

 most anterior portion of the introvert. In sections they are more 

 conspicuous in the middle region of the body than upon the intro- 

 vert, hence the projecting bulb appears more prominent. 



These organs gave a very successful reaction to the blue stain, 

 and frequently single sections were obtained which showed all 

 the details here presented regarding the individual cells and 

 their connection with the main nerves coming from the ventral 

 cord. The number of cells stained by the blue showed consid- 

 erable variation, but the best effects were obtained when not 

 more than six cells had taken the blue color. Organs in which 

 only one or two sensory cells were stained were best for study- 

 ing the peripheral endings (PI. XXXIV, Figs. 4 and 6). The 

 enlarged inner portion of the flask contains a group of bipolar 

 nerve cells very similar in shape to the sensory cells of the 



