67 



is al.tHyg bDriarial by sonae litbls thickness of cytoplasm. The 

 forii is oval or ciroalnr, /lith an alfnost evin contour. Thef? 

 is one large nucleolus, *ith a subsiilary nucleolus in some 

 calls. The nuclear reticuluTi has a rather fine mesh; lar^e 

 granules of chromatin occur at the points of intersection. 



The denirites -arise from the peripheral siJe of the cell- 

 body, and they pass at once into the molecular layer, taking a 

 direct course for the limitans externa. The size of a denlrite 

 is maintained without narkel diminution, the tip, in fact, 

 being so large and blunt as to give a club-like appearance to 

 the 'Whole process. The mode of branching is far simpler than 

 that of the corresponding mammalian neurone. While the den- 

 drite of the latter ramifies to an extraordinary degree, it is 

 rare to fini branching carriei beyond the tertiary divisions 

 in Mustelus; compare my Fig. 13 with Plates 14 and lo of Starr's 

 Atlas ('9^). Prom its greater simplicity, the selachian neu- 

 rone of Purkinje corresponds, in a broad way, to the embryonic 

 condition of the higher form. The branches are spread in one 

 plane, like a plant trainel on a wall, and this plane lies 

 transversely to the cerebellar folds. The course of the branch- 

 es in this plane is less wide than for mammals, causing the 

 whole top to present a markedly more compact appearance. The 

 surface of a denlrite has the conspicuous roughness charfticter- 

 istic of this neurone wherever found. The gemraules, to which 

 this roughened surface is due, are of several different sizes, 

 ranging through mere points through slender spines anJ stouter 



