INTEGUMENT OF NECTURUS MACULOSUS Sit 
after the removal of the tissue, the tail of the living animal was 
examined under a high magnification, and it was found that the 
regenerated epidermis had become completely pigmented, both 
rounded and extremely branched cells: being present, but no 
dermal chromatophores had yet made their appearance. These 
observations confirm the results obtained by Loeb and Strong 
(04) in their studies of regeneration of the skin of the frog, and 
it is evident that the chromatophores of the regenerating epi- 
dermis cannot come from those of the dermis, since the former 
is completely pigmented long before the latter has acquired any 
melanophores. 
d. Evidence from transplantation experiments. This method 
of investigation has been employed by other workers on pig- 
mentation (Loeb, ’97; Winkler, 710 a). Unfortunately, I did not 
begin my experiments early enough to secure conclusive results, 
but even in their incomplete condition they present several 
features of interest. 
Rectangular pieces of pigmented skin, 3 to 5 mm. broad and 
6 to 7 mm. long, were removed from the middle region of the 
side of the tail and patches of white skin of the same size from 
the venter were carefully fitted into the exposed places. In 
one case pigmented tissue was also transplanted to the white 
ventral region. Good unions were secured and in eight to ten 
days an. abundant supply of blood was usually found in the 
grafted tissue. Changes in pigmentation occurred very slowly, 
and two months had passed before any definite evidence of the 
presence of pigment in the white tissue was obtained. At the 
end of four months the pigmentation had extended inward from 
the edge of the patches an average distance of 1} mm., but in 
no case was the entire tissue pigmented. In the regenerating 
tissue, it will be remembered, complete epidermal pigmentation 
had been accomplished within four months. 
In the fifth month one of the white grafts, together with a 
narrow margin of the normal tail tissue, was dissected off and 
fixed. One half was imbedded and sectioned; the other cleared 
and mounted whole. The sectioned material showed that the 
pigment within the originally white patch was confined entirely 
