[20 yournal of Comparative Neurology and Psychology. 



Fig. I. The central nervous system of Prionotus carolinus seen from the left side. Drawn from an 

 alcoholic specimen which had been fixed in potassium bichromate and designed to illustrate the relations 

 of the spinal nerve roots to the sis "accessory lobes" of the spinal cord (Joh. I to loh. 6). The cranial 

 nerve roots are indicated with Roman numerals; t. ac, tuberculum acusticum. X 3. 



Figs. 2 to 15. A series of transections through the spinal cord and medulla oblongata of an adult 

 Prionotus carolinus, from sections stained by the method of Weigert. All are drawn to the same 

 scale. X 12. 



Fig. 2. Section between the fourth and fifth spinal nerves. Areas of unmedullated fibers and neuro- 

 pil are stippled. The enlarged dorsal cornu fills nearly the whole of the dorsal part of the spinal cord. 



Fig. 3. Section through the middle of the sixth accessory lobe (dorsal cornu), showing the entrance 

 of fibers of the dorsal root of the third spinal nerve. The fibers marked desc. sec. tracts are secondary 

 tactile tracts which descend from the sixth lobe and enter the funiculus dorsalis and fasciculus dorso- 

 lateralis farther caudad. The more medial of the tracts thus designated extends backward to become 

 continuous with "funic, dors." of Fig. 2. 



Fig. 4. Section taken between the fifth and sixth accessory lobes, including the most cephalic tip of 

 the sixth lobe. This also disappears, a few sections farther forward, leaving the dorsal cornu practically 

 unrepresented in the section. The dorso-lateral fasciculus is very large, containing, in addition to 

 root fibers of the third spinal nerve, massive medullated tracts between the fifth and sixth lobes. 



Fig. 5. Section taken between the third and fourth accessory lobes. In comparison with Fig. 4, 

 taken between the fifth and sixth lobes, note the great reduction of the dorso-lateral fasciculus. The 

 large size of this fasciculus between the fifth and sixth and fourth and fifth lobes is due to the facts that 

 the third spinal root passes by way of this tract into each of these three lobes and that very large second- 

 ary tactile tracts pass between them. No root fibers pass between the third and fourth lobes and rela- 

 tively few secondary fibers. This indicates that each spinal root supplying the free fin rays is an inde- 

 pendent reflex mechanism within the spinal cord. 



