22 Journal of Comparative Neurology. 



In the tentacles, the cells of the diffuse sense-organs lie in 

 some cases among the basal parts of the bodies of the epider- 

 mal cells. Many of the sense-cells, however, especially in the 

 distal half of the tentacles, lie in the median axis of the latter. 

 It thus happens that the central fibers from these organs do not 

 form a distinct nerve until the base of the tentacle is reached. 

 In sections of the tentacles it is even more difficult than in the 

 palps to locate the position of the epidermal cavity containing 

 each bundle of peripheral processes. It will be noted that in the 

 cephalic cirri (Plate I, Fig. 5 A) the peripheral ends of a few 

 epidermal cells are found attached to the cuticula just within 

 the margin of the inner cuticular cavity. In the tentacles this 

 is carried so far that very slender peripheral ends of epidermal 

 cells almost fill both the epidermal and cuticular cavities and 

 are attached to the cuticula up to and even among the periph- 

 eral processes of the sense-cells (Plate I, Fig. 14). As these 

 cell ends are pigmented, their presence under the perforated 

 membrane obliterates the clear area that rendered it easy to 

 distinguish the position of the epidermal cavity in the cephalic 

 cirri. 



Around each cuticular area, as seen in the removed cuti- 

 cula, is found the same arrangement of groups of larger pores 

 that is found in the palps (Plate I, Fig. 8). 



In the gill-lobes, the diffuse sense-organs are scattered and 

 each contains but a few cells whose bodies always lie in the epi- 

 dermis. The modified cuticular area over each sense-organ is 

 exactly like that found in the cephalic cirri. 



In the parapodial cirri, large numbers of bipolar nerve-cells 

 are stained by the methylene blue and at first sight appear to 

 be isolated cells. But a study of the removed cuticula reveals 

 the groups of fine pores in modified cuticular areas which en- 

 able one to identify the diffuse sense-organs with certainty. 



In sections of the ventral pafapodial cirti, it is clearly seen 

 that the peripheral processes from a few nerve-cells join each 

 other and pass through a slender epidermal cavity to a single 

 modified area in the cuticula (Plate I, Fig. 5B). The bodies of 

 these cells always lie some distance apart and thus give, in sur- 



