322 The Closing of the Wounds in the Larval Necturus 
thinning until at the level of the outer margin of the myotomes it is but 
two layers thick at most, and often but a single layer. This thinning of 
the epidermis has been noted by Barfurth in Rana and Siredon. Not 
only is there a thinning of the epidermis through some sort of cell move- 
ment, but also the cells remaining as the single covering layer, often 
show a decided thinning through rotation and elongation. 
The cells in the thickened margin show some peculiarities. They seem 
to be less compact than in the normal epidermis, their cell boundaries are 
not well defined and their cuticular margins are indistinct. The gland 
cells are readily distinguished in sections through their large size and 
numerous coarse yolk granules. The mitoses appear about as frequently 
as in the normal. The changes in the dermis are slight, the chromato- 
phores show little if any movement toward the wound. It is impossible 
to say to what extent the dermal tissues are involved, such as blood- 
vessels, lymphatics, connective tissue, etc., owing to the fact that it is 
impossible to follow their changes closely enough in the sections. 
The next section studied is from a larva at a stage corresponding to 
that shown in Fig. 3. At this time the margins of the original wound 
are clearly defined through the position of the chromatophores (Fig. 6). 
The epidermis has continued its movement toward the median line. The 
free margin of the epidermis is rounded and as in the preceding stages, 
is six or seven layers in thickness. Toward the periphery, at the outer 
margin of the myotome, the epidermis does not show the marked 
thinning which was observed in the preceding section, but is about the 
same thickness as in the normal larva, although there is no indication of 
a decided increase in the number of mitotic figures. The cell boundaries 
are poorly defined. The cuticle is more distinct than in the preceding 
stage and the gland cells are still present. 'The dermis shows no marked 
change either in movement of chromatophores or other structures. 
A section representing the condition as observed some 90 minutes alter 
cutting is shown in Fig. 7. The margins of the epidermis still show a 
decided thickening. In the dorso-lateral regions, the epidermis is not 
completely restored to its normal thickness. At this time the margins of 
the wound, are not only in close contact, but also have fused at their 
ventral edges. This fusion is brought about, so far as can be seen, by a 
simple coalescence of the cuticle-free margins of the thickened portions 
of the epidermis. The gland cells are present in the same relative num- 
bers as in the preceding stage, as are also the mitotic figures. In some 
cases the closure of the wound does not take place precisely as outlined 
above, but a narrow band of cells extends between the thickened margins 
