620 PKOCEEDINGS OF THE AMERICAN ACADEMY. 



It may l)e noted in this connection that a greater number of nerve 

 fibers are impregnated in the region of the muscles than in the neigh- 

 borhood of the neural tube. This might be due to any one of several 

 conditions; e. g., a fiber may change in character before it reaches 

 the neural tube, thus presenting for impregnation different conditions 

 in its two parts; or branching may take place more freely than my 

 specimens indicate. Perhaps the mechanical tension on the nerves, 

 between their exit from the neural tube and the nearest point of the 

 muscle, due to the action of reagents, may destroy, or render unsuita- 

 ble for impregnation, that part of the nerve. 



The motor endings shown in Figures 27, 28 (PI. 5) and 43-45 (PI. 8) 

 are probably fairly typical. They agree in size and form with those in 

 gold-chloride preparations, and the surrounding muscle does not show 

 the deposit of silver sometimes evident in material impregnated by 

 the Golgi method. These endings were found in nearly all portions 

 of the side muscles except the region adjoining the skin. They are 

 present in considerable numbers a short distance from the exterior. 

 Many endings were found dorsal to the neural tube, not far from the 

 dorsal fin. I was unable to trace motor fibers into the neural tube 

 beyond its sheath. No preparations of any kind showed motor fibers 

 continuing in the neural tube in the manner figured by Dogiel in his 

 Figur 45. In certain preparations, not cut in a true frontal plane, 

 fibers appeared to end some distance inside the sheath of the neural 

 tube, but on further study this proved to be an illusion, caused by the 

 direction of the section. I am inclined to believe that the true course 

 of motor fibers in the neural tube is as vet undiscovered. 



