Art. ii.j Herrick, Gjistatory Paths in Fishes. 47 



sensory roots of the IX and X nerves penetrate at once to its 

 deeper layers and then turn outward to end near the surface 

 much as will be described in Ameiurus. In Cycleptus the lobe 

 is larger and the sensory roots penetrate but little before they 

 spread out to end in a superficial layer of large cells which stain 

 very pale in haeniatoxylin. And in the carp (Fig. 5), whose 

 vagal lobes are still more enlarged, the greater part of the sen- 

 sory roots do not penetrate, but spread out over the whole 

 outer surface of the lobe (constituting Mayser's first layer), 

 thence to pass in separate strands directly into a thick layer 

 exhibiting alternate bands of crowded small cells and dense 

 neuropil (Mayser's second layer). 



This will be termed the layer of secondary neiirones. Sec- 

 tions stained by Delafield's haematoxylin show within it 

 seven concentric bands of cells and neuropil which are more or 

 less sharply distinguishable, of which the two outer are of 

 greatest importance. The first is a thin layer of crowded ceils 

 of relatively large size which take up a very pale stain — the 

 chief secondary gustatory neurones. Immediately internal to 

 and among these cells are smaller very closely crowded cells 

 whose nuclei take up a very intense stain. These will be 

 termed the smaller gustatory neurones. The other bands con- 

 tain chiefly minute cells with deeply staining nuclei and occa- 

 sionally larger, irregularly shaped cells among them, while the 

 inner border of this layer is a band of neuropil containing a iew 

 large cells which take a very pale stain. Sections stained by 

 the method of Pal show sensory root fibers entering this band 

 at its inner border. These root fibers will be termed the deep 

 communis root of the vagus, as distinguished from the larger 

 superficial root (Fig. 5). The fibers of the deep root turn out- 

 ward to end in the second layer along with those of the super- 

 ficial root. 



This layer of secondary neurones is very wide in Cyprinus 

 and is traversed radially by unmeduUated and delicately medul- 

 lated fibers for the deeper layers of the vagal lobe. The large 

 pale cells forming its outer boundary are the most important 

 and characteristic cells of the lobe, for they give rise to the 



