284 



FISH. 



EXPLANATION OF PLATE XV. 



Fig. 37. Transection through the myel and spinal ganglion to show the fibers 

 and the passage of the dorsal root-fibers into the myel. X 190. 



Fig. 38. Shows the precocious division of the ventral root. From near the 

 middle of the length of the body. X 190. 



Fig. 39. Cell from the roof of the mesencephal. X 190. 



Fig. 40. Multipolar cell from the oblongata. X 190. 



Fig. 41. Cell from the occipital region of the cerebrum. X 190. 



Fig. 42. Cell from the mesencephal. Nerve cells, with their processes mostly 

 branching at the alba. X 190. 



Fig. 43. Transection of myel ; tail region. X 190. 



Fig. 44. Transition cells from the mesencephal. X 190. 



Fig. 45. Multipolar cell from the oblongata. X 190. 



Fig. 46. Transection of the cerebellum, to show the beaded or varicose condi- 

 tion of the fibers. X 190. 



Fig. 47. Cell from the dorsal portion of the myel, with its neurite crossing to 

 the opposite side ; near the vent. X 190. 



Fig. 48. Transection of myel, to show a transitional form of cell located at the 

 margin of the entocinerea; just caudad of the arms. 



Fig. 49. A transition cell. X 190. 



Fig. 50. Frontal (horizontal) section of myel. X 190. 



Fig. 51. Region of mesencephal, to show the division of the cell-processes at 

 the alba, and occasionally in the cinerea. X 190. 



Fig. 52. Transection through the Gasserian ganglion of the Petromyzon, show- 

 ing transitional stages of the ganglion cells; one of the cells is connected with 

 three processes. X 190. 



Fig. 53. From the mesencephal, similar to Figs. 42 and 51. X 190. 



