81 



example, List states that " the neurofibrillae split in the 

 epithelium into several branches, form richly branched 

 networks, and send some fibrillae through the cuticle to 

 the outside. Since, however, every fibril does not pass 

 beyond the cuticle, but often only goes as far as its outer 

 edge, one can easily get the impression that the 

 osphradial epithelium was ciliated with very delicate 

 cilia which have partly fallen away in fixation." This 

 pseudo-ciliated margin is, then, the cuticle with its 

 numerous neurofibrillae. 



Bernard merely states that there is an inter-epi- 

 thelial network of nerve fibrils, and leaves one to assume 

 that these are all connected with neuro-epithelial cells. 

 The real case is as follows: — Below the epithelium runs 

 the nerve, and with the nerve fibres are multipolar 

 ganglion cells. From these multipolar cells delicate 

 neurofibrillae pass out and enter the epithelial region. 

 Here they branch in all directions and finally reach the 

 surface. They run through the cuticular seam in a 

 parallel manner perpendicular to the plane of the epi- 

 thelium and appear, therefore, as striae in sections. 



So far, Hanvier's gold methods have not been used, 

 and Bernard's neuro-epithelial cells have not been 

 actually re-investigated by the methods he used. The 

 nerve network with the free nerve endings is, however, 

 present and is without doubt the important sensory 

 structure in the organ. By ordinary methods and 

 macerations no obvious or numerous sense cells were 

 found. The structure is, in my opinion, identical with 

 that of the lamellibranch osphradium. 



Little need be said about the non-sensory epithelium 

 of the leaflets. The ciliated band (fig. 45, Osp. cil.) is 

 about ten cells broad, the cells differ from those of the 

 sensory area in being compact, more cylindrical, and with 



