30 MATHILDE M. LANGE 
and the axial nerve, grow so quickly and appear as differentiated 
myelin fibers in the most distal portion of the regenerated piece, 
while all the surrounding tissues are still in blastemal stage, is 
a strong argument in favor of this theory. On the inner side 
of the myelin cords the neuroblasts form the same regular rows 
as the ganglion cells in the normal arm. Eleven days after 
operation this regular arrangement and also the tissues separat- 
ing these rows were visible. The first sign of the new central 
mass of nerve fibers also appears at the same time. The myelin 
cords probably produce the first fibers of the new neuropil, for 
the young nerve cells do not at this time exhibit any processes. 
Only later are the neuroblasts turned into ganglion cells by forming 
protoplasm and fibers. As the differentiation of the ganglia 
progresses, the neuropil naturally gains in size. Three weeks 
after operation the axial nerve is well developed in all of its three 
components (fig. 38). Among the ganglia the small cells, the 
so-called nude nerve nuclei, predominate. But there are also 
quite .a number of medium-sized nerve cells present, whereas 
large ganglia are still missing. The latter probably appear very 
late, for I was unable to find any, even in regenerated pieces, 
which were already in quite an advanced stage. The young 
neuropil contains relatively many nuclei, which, however, de- 
crease in numbers as development goes on. The greater part 
of the regenerated piece is occupied by the axial nerve, the rest 
of the tissues being confined to a relatively small space. The 
same conditions prevail in the embryonic arm. In the normal 
arm the axial nerve constitutes a fourth part of the whole.® 
Unfortunately, I was not able to observe the formation of 
the sucker ganglia and the four nerve cords embedded in the 
muscles. The sucker ganglia probably appear very late in the 
regenerated piece, for I was not able to find a single one. I 
believe their formation is only initiated after the nerves which 
connect the axial nerves with the sucker ganglia and also inner- 
vate the suckers have grown out from the axial nerve. It is 
5 JT should like to draw attention to the publications of Brynes and Fritzsch. 
Both of them studied regeneration in water newt (Triton) extremities and found 
that cartilage is evolved from blastema directly opposite of the growing nerve. 
