1. The dark longitudinal stripe (expanded melanophores) produced in the tail of Fundulus by a transverse denervating cut of 1 mm. length appears about half a minute after the cut is made, it reaches its maximum development in about an hour, and fades to the lightness (contracted melanophores) of the ordinary light fish in from 22 to 96 hours (average 297 hours).
2. A dark longitudinal stripe similar to that described in paragraph 1, but from a 2 mm. cut, fades after 43-143 hours (average 78.3 hours).
3. Light-tinted fishes, such as are noted in paragraphs 1 and 2, when put on a dark background, become fully dark, except for the stripe on the tail, in about 1.8 hours. Under such circumstances a 1 mm. stripe becomes dark within 17-27 hours (average 20.5 hours) and a 2 mm. stripe within 23-70 hours (average 37.4 hours).
4. Dark-tinted fishes, when put on a light background, become fully light, except for the stripe on the tail, in about 4.6 hours. Under such circumstances, a 1 mm. stripe becomes light within 18-31 hours (average 26.4 hours) and a 2 mm. stripe becomes light within 22-86 hours (average 51.6 hours).
5. The darkening of the stripe (expansion of melanophores) and the fading of the stripe (contraction of melanophores) cannot be due to the nerves of the stripe, for these have been cut. The changes in colour are due to the gradual passage of an expanding neurohumor or of a contracting neurohumor from the adjacent regions into the stripe.
6. This gradual change is much too slow for blood or lymph. It is believed to be due to a cell-to-cell transfer.
7. Transfer of substances from cell to cell has been observed in plants (Kok), occurs in coelenterates, and is seen very probably in a number of instances in the human skin (spread of inflammation from radiated areas, erysipeloids, insect stings, and possibly vitiligo).
8. Cell-to-cell transmission is a relatively slow process. Phylogenetically, it antedates transmission by blood and lymph.