40 



BRISTOL. 



[Vol. XV. 



lies much closer to the mass and exhibits more of the characters 

 of the normal cells found in the body ganglia. 



In the "anal ganglia" (PI. VI, Figs. 14 and 15, and Fig. i in 

 the text), the first neuromere, XXV, the cell is normal. In 

 the second, XXVI, the two nerves partly fuse at a little 



distance from the margin, 

 and continue thus for a 

 short distance, when they 

 become fully separate. 

 Within this region of par- 

 tial fusion " Leydig's cell " 

 is found lying between the 

 two trunks compressed and 

 changed into a spindle- 

 shaped cell ; the prolonga- 

 tions extending median 

 and lateral as in the cells 

 of the first four neuro- 

 meres. In the third "anal" 

 neuromere, XXVII, the 

 cell appears in the same 

 relative position, but is 

 more compressed and elon- 

 gated. Good histological 

 preparations of these cells 

 show that the size and 

 structure of the nucleus 

 and the nucleoli are iden- 

 tical with those of a cell 

 from a mid-body region. 

 The fourth, XXVIII, and succeeding neuromeres, XXIX 

 to XXXIV, innervate the sucker. The fusion here is as com- 

 plete as in the first four neuromeres, and the " Leydig's cell " 

 has been pushed out, in the more complete fusion of the nerve 

 trunks, until it lies completely outside of and upon the nerve, 

 about midway from the anal ganglion to the edge of the 

 sucker ; the prolongations extending, as before, median and 

 lateral. In these most posterior neuromeres the size and 



TEXT-FrG. I. — The four anterior neuromeres of the 

 " anal gangUa " seen from the ventral side, showing 

 the stages of compression of " Leydig's cell " till it 

 appears outside of the fused trunk in XXVIII (ist 

 anal in Clepsine) and the succeeding nerves. ( From 

 a camera drawing of a nitric acid preparation. 

 The details of the " Leydig's cell " were supplied 

 from sections.) 



