ae A. B. DAWSON 
to the epidermis. No change whatever had taken place in the 
chromatophores of the dermis of the tissue surrounding the 
graft, although good connections had been established in this 
stratum. There was, however, an abundance of leucocytes in 
the dermis of the transplanted skin, and near its margins numer- 
ous small cells containing pigment were seen. It was not pos- 
sible to decide whether the pigment in the epidermis was due to 
an immigration of chromatophores or whether it had developed 
in situ owing to some influence. which was exerted by the sur- 
rounding pigmented tissue. The half which had been mounted 
whole gave a clear idea of the distribution of the chromatophores 
in the white patch. They were especially numerous near the 
margins, and cells without processes predominated. Nearer the 
center of the patch the cells were usually less densely pigmented. 
This condition argues against the idea of an immigration of 
chromatophores, since, if pigmentation occurred in that way, 
we should expect to find chromatophores of equal density in 
all parts of the newly pigmented region of the graft. Of course, 
this objection could be met by assuming that the less heavily 
laden pigment cells were more active than the dense chromato- 
phores. Two other patches, examined on the living animals, 
also showed the cells with the least pigment to be nearest the 
center. The highly branched types were present and most of 
them were near the edges. In the fixed material many were 
greatly elongated and showed a definite orientation radially 
from the center of the patch. 
The dark graft on the white venter was observed closely: For 
a long time after the operation no change in it was detected, but 
at the end of ten weeks a small light area was noted near its 
center. This area steadily increased in size and, at the time 
observations were discontinued, appeared as a large irregular 
region extending in places almost to the margins of the patch. 
When examined under a low power of the microscope it was seen 
that the light appearance was due to the absence of the dermal 
chromatophores. The epidermal chromatophores, however, were 
still present and a few could be seen scattered through the white 
tissue in the immediate vicinity of the transplanted pigmented 
portion. 
