OCTOPUS ARM, REGENERATION AND STRUCTURE 5) 
The nervous system of the arm is quite complicated, and is 
composed of three distinct parts, viz., the central or axial nerve, 
the group of ganglion cells situated above each sucker, and the 
intramuscular nerves. The complex structure of the axial nerve 
has given rise to much scientific discussion. Van Beneden (’90), 
Cheron (’66), Owsjannikow (95), and Kowalewsky claims that 
the axial nerve is a part of the peripheral nervous system, whereas 
Colosanti (76), Uexkull (93), and Guerin (’08) maintain that 
its qualities in structure, as well as in function, are such that it 
would easily be compared to a central nervous system. The 
three components of this complex axial nerve are: 1) a layer of 
ganglion cells; 2) a centrally located mass of nerve fibers, and, 
3) two myelin cords running along the back of the arm. The 
ganglion cells are surrounded and supported by glia tissue. This 
tissue also forms a sheath around the processes of the ganglion 
cells and is present in the mass of centrally located nerve fibers 
(fig. 3). 
Each arm is provided with one main artery embedded in the 
connective tissue, which les between the two. myelin cords. 
Two large veins (venae brachiales superficiales) running along 
the external side of the arm in the dermal layer, form the two 
main components of the brachial venous system. Little veins 
from the inner side of the arm convey the blood from the vicinity 
of the suckers to the two large afferent vessels. The blood of 
the Cephalopoda is a thin liquid containing only one kind of 
blood-corpuscles. The latter have some similarity to the leuco- 
cytes of the vertebrates. Kollman (08) gave a detailed descrip- 
tion of them (fig. 4). The blood has no fibrinogen. ’ 
REGENERATION 
1. A study of the external changes taking place during regeneration 
In the introduction attention has been called to the fact that 
the regenerative power of the octopus arm has been revealed 
by the discovery of many animals having regenerated arms. 
The authors who have reported on such specimens have also 
been mentioned. The embryonic development of the arm has 
