No. I.] THE METAMERISM OF NEPHELIS. 53 



on the dorsal side, four on the ventral side. These cells 

 resemble in size and character of nucleus the "Leydig's cell" 

 of the body neuromere. They all send fibers in both directions 

 into the ring, but I have been so far unable to follow them 

 to their terminations. The groups differ in characteristic 

 features, and for the purpose of description I have named them 

 as shown in the figure. They are constant in their position 

 and character throughout the leech, and this I determined by 

 comparing the six rings in three successive mid-body metameres 

 minutely, detail with detail, by the method described in the 

 early part of this paper. 



The inner dorsal group (in. d. bpc.) consists of one bipolar 

 cell with a short pedicel, lying in the 3d muscle bundle 

 almost sessile on the ring. The outer dorsal group {o. d. bpc.) 

 consists of a cell with a very long pedicel, lying in the 4th 

 muscle bundle. The lateral dorsal group {lat. d. bpc.) consists 

 of six or eight cells, four to six of which are small, lying in the 

 outer or 6th muscle bundle. 



The outer ventral group {0. v. bpc.) consists of one cell with 

 a short pedicel, lying in the 5th muscle bundle, and like the 

 inner ventral group, very near the point of junction with the 

 nerve trunk from the central system. The inner ventral group 

 {hi. V. bpc.) consists of two or three cells with pedicels of 

 medium length, lying near the edge of the 4th muscle bun- 

 dle. The connection with the central system at this point is 

 different from the others. The trunk divides just before reach- 

 ing the ring, and as I have traced fibers from this inner ventral 

 group into that branch nearest the group, it is evident that it 

 carries fibers from these cells to the ganglion, the sensory 

 fibers, while the other branch of the nerve trunk carries motor 

 fibers from the ganglion into the ring. If my data as just 

 given are sufficient, then we have the same morphological con- 

 ditions that obtain in the spinal ganglion of vertebrates. The 

 one piece of evidence wanting is the termination of the other 

 pole of the cell. These cells are without doubt those which 

 Retzius (/. c.) sought, as quoted above (page 42), to find in 

 the epidermis. These cells, together, possibly, with the outer 

 ventral cell, answer the conditions called for by Retzius for 



