538 H. LYSTER JAMESON, 



cells (c. c) lying between these ; 3) large unicellular skin-glands, 

 cbiefiy distributed on the summits of the papillae and on the pro- 

 boscis (Figs. 2 and 5 gï), and 4) sense organs (Fig. 6). Owing to 

 the reduction of the papillae on the proboscis, the first, second and 

 third types of cell are here fairly equally distributed, but on the body 

 itself this is not the case. In the grooves and furrows between the 

 papillae of the body the two first types alone are represented. We 

 have in such places a fairly typical Annelid epidermis showing an 

 alternation of deeply and faintly staining cells (Fig. 1), which may 

 be compared to the "Fadenzellen" and "Plasmazellen" of the Capi- 

 tellidae^ as described by Eisig (4). 



On the papillae themselves (Fig. 2) the nature of the epi- 

 dermis is very diflerent, owing to the enormous development of the 

 great gland cells. These latter occur in such numbers as to greatly 

 distort the whole epithelium in many places, and my observations, 

 although 1 have devoted much time to the study of these papillae, go 

 but a part of the way towards the complete elucidation of their struc- 

 ture. The "Fadenzellen" {ep. c) are here very much drawn out between 

 the gland cells, giving in many places an appearance of sensory 

 organs in connexion with underlying tissues. 



This appearance of sense organs is, I believe, in great part de- 

 ceptive, being comparable to the instance described by Ward (19), in 

 Sipunculus, where he holds that a similar state of affairs has resulted 

 in the description of such sense organs. W^ard says (p. 149): "Often 

 when these cells are crowded and distorted by near-lying glands 

 one is inclined to believe in an actual continuity of cell and fibre 

 which cannot be demonstrated, and which, so far as I could find, is 

 not present in less confused regions." 



I believe that in great part the connexion of the epithelial cells 

 with a "réseau ganglionnaire" described by Rietsch (12) is referable 

 to such a distortion of the epidermis. To this matter I will return 

 later. At the same time we must allow for the possibility of such a 

 connexion existing in a limited degree. Although the majority of the 

 sense organs that I found occurred on the proboscis, I believe that I 

 have more than once seen such structures on the body papillae, but 

 the compression and distortion of the tissues did not allow me to 

 be certain of their relations. 



In many places, also, there are intercellular spaces between the 

 "Fadenzellen" probably due to the methods of preservation employed. 

 These spaces are not always easy to distinguish from "Plasmazellen" 



