510 A. B. DAWSON 
In Necturus the problem is rather complicated, since it is 
difficult to decide whether or not we are dealing with but one 
type of pigment cell. Eycleshymer’s observation, while not 
conclusive, seemed to indicate that the cells have different 
origins, but, as he remarks, they may be the same kind of cells, 
merely acquiring pigment in different regions of the body. In 
my examination of several hundreds of slides I have found many 
conditions intermediate between the pyramidal cells and the 
more highly branched forms, suggesting that the latter were but 
extreme expansion phases of the former. In one case also (fig. 
2) a large mass of cytoplasmic material was observed within 
the body of a cell which would ordinarily be regarded as a well- 
defined epidermal chromatophore. The facts presented suggest 
that we are dealing with but one kind of cell which may at differ- 
ent times be completely rounded, slightly expanded or very 
highly branched. 
c. Conditions in regenerating skin. The adult Necturus pos- 
sesses but small capacity for regeneration andthe process is 
very slow. Where pieces of tissue were removed from the thin 
edge of the tail, regeneration proceeded gradually, but the gap 
was never entirely filled. Sections of this new tissue, made 
eight days after the operation, showed that the epithelium had 
moved outward over the wound, carrying with it chromatophores 
and ordinary pigmented epithelial cells. The chromatophores 
were usually without long processes and typical highly branched 
cells did not usually appear until some time later. 
In regeneration the connective tissue lags far behind the 
epidermis, and in several cases eight weeks after the operation 
no dermal chromatophores had been developed. Occasionally 
I found small cells bearing pigment granules in the newly formed 
connective tissue. They may be leucocytes or developing 
chromatophores. In the epidermis, however, chromatophores 
were very plentiful. ‘Two were found in mitosis in regions where 
rapid proliferation of ordinary epithelial cells was taking place. 
Both possessed long processes. / 
Pieces of skin (3 x 5 mm.) were removed also from the side 
of the tail for use in transplantation experiments. Four months 
