346 FLEXNER. 
EXPLANATION OF PLATE XXVIII 4. 
Fic. 1. Semi-diagrammatic representation of the nervous system of Planaria 
torva. A.A. nervous ganglia; &.4. nervous cords. Ganglion cells indicated in 
gray. 
Fic. 2. Karyokinesis in cells adjacent to the site of injury. The greatest 
activity in and increase of cells is near the ectodermal covering. Two fields are 
shown, A. near, &. somewhat removed from the injury. 12 to 18 hours after 
decapitation. 
Fic. 3. Newcells at the site of injury. Pushing forward of the cells to cover 
the defect, the new elements becoming continuous with the ectodermal cells. 
Large, thin, protoplasmic masses (syncytium) cover the extreme edge. A.A. cells 
pushing forward to epidermis; 2.4. syn¢ytium; C.C. masses of newly formed 
cells. 12 hours after decapitation. 
Fic. 4. A nerve cord (4.) surrounded by new cells. The thickest group 
covers the cut end, and individual cells of the same type may be seen pushing 
their way among the fibers. Indistinct fibrillae appear between the cells above 
the cord. 48 hours after decapitation. 
Fic. 5. Completion of the ganglion. Increased richness of cells on each 
side of the cord and normal radial arrangement around the bulbous end. Differ- 
entiated nerve cells show a lighter tone than the remainder. After 60 hours. 
Fic. 6. Completely regenerated nervous system. 4.d. ganglia; 2. commis- 
SUIe; 9G: C. nervous cords. After 4 days. 
Fic. 7. Showing neuroblasts next to and beyond the sectioned nerve cord. 
Only the cells in close proximity to the original cord exhibit processes. 
Fic. 8. Complete double-headed form. A.A. nerve cords; £&.28. ganglia. 
The new ganglia on each side are united by commissures, and to each pair a single 
cord is attached. Eye-spots shown. 
Fic. 9. Almost completely regenerated longitudinally divided half. 4.4. 
ganglia; B.B. cords. The cord &.1 not quite perfect. After 13 days. 
