268 HANDBOOK OF INVERTEBRATE ZOOLOGY. 



(i.) The external sheath, with a few scattered nuclei 

 upon its inner surface. 



(ii.) The nerve, made up of a number of parallel fibres. 



(iii.) These fibres may be traced into the ganglion, 

 where they diverge from each other. 



d. In the ganglion are : 



(i.) An outer transparent layer (>). 



(ii.) A more opaque pigmented portion (c). 



e. In the transparent portion are a number of highly 

 refractive spindle-shaped bodies (e) with an outer rounded 

 and an inner pointed extremity. 



(i.) From the pointed end a fine, transparent, highly 

 refractive fibre or rod (f) runs backwards, and may be 

 traced nearly to the opaque portion of the ganglion. 



f. On the anterior or distal surface of the opaque por- 

 tion are a number of highly refractive oval bodies, the 

 nuclei (</), arranged in a single row. 



g. Back of these the mass of the opaque portion (i) of 

 the ganglion is made up of crowded, spherical, somewhat 

 granular ganglion cells (/*), which are embedded in the 

 granular substance of the ganglia, so that their outlines 

 are not readily seen. 



13. When the fresh ganglion is torn to pieces with 

 needles, and the fragments examined with a high power, 



a. The spindle (Fig. 14, A, a) is seen to be a sharply 

 defined body, made up of a transparent, highly refractive 

 outer layer and a central granular core. 



b. The pointed end of the spindle is continuous with the 

 rod (6), and wherever the latter has been disturbed by 

 the needles it is bent abruptly at an angle, thus showing 

 that it is brittle and inflexible. The rod is transparent 

 throughout the greater part of its length. 



c. The posterior or inner end of the rod is opaque, 



