REGENERATION IN ANNELID NERVE CORD 171 
formation is due to similar conditions. The molluse plug is due 
to the thick mass of agglutinated cells holding back the further 
flow of liquid, rather than to the formation of a true clot. 
The plug which forms at a cut in the earthworm may be 
thought of, then, as a large mass of agglutinated cells, filling 
all the wound region and attached to all raw surfaces through 
this same power of agglutination. The subsequent shrinkage 
of the cytoplasm brings the nuclei closer together, giving the 
plug a denser appearance and also draws the cut edges toward 
each other through shortening of the cytoplasmic strands. 
A comparative study of cells from the cicatrix of different 
stages shows some very interesting results. The cells from an 
early cicatrix (fig. 9, forty-five mimutes’ regeneration) show a 
marked similarity to the agglutinated cells of the blood smear, 
both in size and staining reactions. With two days’ regenera- 
tion (fig. 10) the cells are smaller and more compact, while the 
cytoplasm shows definite fiber formation. With further growth, 
the ‘cells show still more condensation, and the fibers become 
orientated in the direction of pull of the muscle layers and nerve 
cord. A comparison of figures 12, 18, 14, and 15 shows this 
continuous growth of cicatrix cells and fibers and their relations 
to other layers of the body. Figure 12, of ten hours’ growth, 
shows large round nuclei. Figure 13, a day and six hours’ 
regeneration, shows a condensation, with definite fiber growth 
and orientation. At one day and twenty-one hours the cells are 
still smaller (fig. 14), while at three and a half days (average 
time for recovery of normal movements after section of the 
cord) the fiber growth and orientation show a distinction in form 
for the two muscle layers (fig. 15, L. M. F. and C. M. F.). 
A study of blood smears and films and a comparison of the 
cells found there with the cells of the cicatrix at different stages 
of regeneration lead to the conclusion that the plug is a mass of 
agglutinated blood corpuscles whose cytoplasm forms definite 
fiber connections with all raw surfaces and, through subsequent 
shrinkage and orientation, like tissues become united and func- 
tional in a very short period.of time. 
