UNIVERSITY OF CALIFORNIA PUBLICATIONS 



IN 



ZOOLOGY 



Vol. 13, No. 7, pp. 167-174, plate 10 August 4, 1914 



THE MOVEMENTS AND REACTIONS OF THE 

 ISOLATED MELANOPHORES OF THE FROG 



BY 



S. J. HOLMES 



The observations previously reported by me (1913) on the 

 movements of isolated pigment cells derived from the embryos and 

 young larvaj of amphibians showed that these cells undergo marked 

 changes in outline, and frequently creep for a considerable distance 

 away from the tissue in which they were embedded. The hanging- 

 drop cultures in which these cells were studied presented exceptionally 

 favorable conditions for observation which rendered it possible to 

 determine, without the least uncertainty, that the pigment cells 

 changed in an amoeboid fashion, that the processes of ectoplasm that 

 were formed were very quickly invaded by pigment granules, and 

 that the distribution of pigment within the cell gave a fairly faithful 

 picture of the outline of the cell itself. The old question as to whether 

 the changes that may be observed in pigment cells are due to changes 

 in the outline of the entire cell or to the flow of pigment within cell 

 processes which remain comparatively unchanged is therefore to be 

 decided, for the forms studied at least, in favor of the former view. 



It would not be safe, however, to draw the same conclusion in re- 

 gard to the pigment cells of the adult animals, especially since so 

 many investigators have convinced themselves of the opposite inter- 

 pretation. Studies of the behavior of pigment cells of other animals 

 in places such as the transparent fins and tails of fishes where they 

 could be readily observed, have led several observers to the conclusion 

 that pigment may flow back and forth within processes of pigment 

 cells which may be followed more or less clearly despite their trans- 

 parency. Following the cell processes of a chromatophore when they 

 are devoid of pigment is usually very difficult, and in most cases 



'J 



AUG 14 L.:. 



