OCTOPUS ARM, REGENERATION AND STRUCTURE 2t 
inhibiting elements appear in the nerve cell which prevent its 
further division. In the following I shall try to give a short 
histological study of nerve regeneration in the arm of Octopus 
vulgaris. 
An examination of the wound with a magnifying glass im- 
mediately after operation reveals the fact that the axial nerve 
protrudes beyond the surrounding tissues (fig. 4). H. Miiller 
found similar conditions in the spinal cord of a lizard whose 
tail had been amputated. An intense and active degeneration 
is initiated in the protruding part of the axial nerve. This 
‘ disintegration progresses so quickly, that it is very difficult to 
make a thorough examination of its various stages. It begins 
in the layer of ganglion cells. The first signs of degeneration 
become visible in the nucleus. The chromatin, which in the 
normal nucleus is generally thickest along the periphery, moves 
toward the center and gathers around the nucleolus, the nuclear 
membrane still retaining its original form while this process is 
going on (fig. 35). Later on this membrane also degenerates, 
and the nucleus, which has in the meantime shrunk to a homo- 
geneous little lump, lies in a kind of vacuole. Most of these 
nuclear remnants soon disappear, but some of them seem to be 
endowed with a great power of resistance, as they are still present 
even after a few days. I was not able to observe carefully 
the degeneration of the protoplasm. On the whole, I found the 
endoplasm resisting longer than the ectoplasm. The nuclei of 
the glia tissues shrink and are changed into homogeneous chro- 
matin globules, resembling the reduced ganglion-cell nuclei, only 
somewhat smaller in size. The degeneration in the neuropil 
is at first not as marked as in the ganglia layer, and is only 
noticeable by a slight disintegration of the tissues. When 
stained with eosin, the neuropil no longer exhibits the same 
intense coloring as before, and the glia nuclei distributed in it 
have noticeably shrunk. The fibers of the myelin cords are 
swollen and unduly enlarged at the distal end of the stump. 
Sometimes they are from four to six times as voluminous as the 
normal fiber. The myelin, which in the normal fiber is so 
equally distributed as to give it a homogeneous appearance, 
THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 31, No. 1 
