Vol.. 8, 1922 
ZOOLOGY: W. H. COLE 
31 
by regenerated host tissue. From these facts it is concluded that the 
integument of frog tadpoles is locally specific, and self -differentiating even 
when transferred to a new soil on the same animal. 
3. Auto- and homoio-transplants of white belly skin on the dark back 
regions always acquire melanophores. The process varies according 
to the source of the transplant. In auto-transplants there is no antagonis- 
tic reaction between the protoplasms of the graft and the host, and union 
is quickly established. Melanophores appear only after several weeks, 
sometimes months. They are accompanied by the appearance of an 
abundance of scattered melanin granules and irregular masses of pigment, 
which may readily be interpreted as due to the presence of "young" mel- 
anophores. In homoio-transplants, union is delayed by the action of the 
homoio-toxin. In an effort to cover the wound as soon as possible, the 
surrounding epidermal cells migrate rapidly over the wound, and over the 
graft as though it were a foreign body. Melanophores are carried along. 
Such epidermal pigmentation may occur within twenty-four hours. Sub- 
sequent increase in the number of epidermal melanophores and the appear- 
ance of dermal melanophores and xantholeucophores are caused by forma- 
tion in situ as a result of the normal growth activity of the integument. 
It may therefore be said that in auto-transplants the acquisition of 
melanophores is chiefly the result of formation of pigment from the epi- 
thelial cells in situ, while in homoio-transplants the pigmentation is chiefly 
the result of epidermal migration which carries along melanophores. It 
may be followed by formation in situ. 
4. When the conjunctiva of frog tadpoles is extensively injured by 
scratching or pricking, the regenerated tissue is pigmented first by epi- 
dermal melanophores and later by dermal melanophores and xantholeuco- 
phores. Such pigmentation, which may obscure the eye and presumably 
impair vision, persists indefinitely. It is further proof that no regulatory 
action between the eye and the overlying skin exists in tadpoles over 20 
millimeters in length. The method of appearance of the pigment throws 
further light on the question of epidermal wound healing. The extensive 
injury of the conjunctiva compels the surrounding skin to repair the wound. 
The epidermal cells migrate over it and carry along the melanophores. 
Subsequent increase of pigment results from mitotic multiplication of 
integumentary cells. 
5. A series of experiments was performed to discover the stimuli causing 
expansion and contraction of the dermal melanophores. Briefly, it was 
found that expansion is caused by a low temperature (near 0° C.) inde- 
pendently of illumination; by darkness; by a 0.1% chloretone solution; 
by anoxemia and by a low metabolic rate coincident with a moribund 
state. Contraction of the dermal melanophores is caused by a high 
temperature (near 35° C.) independently of illumination; by light, and 
