521 



and contracted phases. Camera-lucida drawings, however, of a single 

 chromatophore, showed that after a contraction of twenty hours, the 

 processes had not been changed in any way; the expanded chromato- 

 phore had the same contour as before the contraction (Textfig. 1, 

 a-c, p. 23). 



Kahn und Lieben (:07) made series of consecutive photographs 

 of single melanophores in the web of the frog's foot (R. temporaria). 

 These cells Avere first photographed in the expanded condition; they 

 were then contracted by an intra-venous or intra-peritoneal injection 

 of adrenalin (Lieben : 06), again photographed, and, after recovering 

 from the effect of this contracting stimulus, the re-expanded melano- 

 phores showed pre- 

 cisely the same con- 

 tours as in the first 

 expanded phase. 

 Altho these observa- 

 tions proved conclu- 

 sively that the mela- 

 nin granules migrate 

 along fixed paths, 

 Winkler (: 10), after 

 a series of experi- 

 ments with Hyla ar- 

 borea, seemed in- 

 clined to revert to 

 the older view of 

 FiCALBi ('96), who 

 believed that the chromatophores have the power of sending out new 

 processes which are independent of the preformed paths. Winkler 

 used galvanic and induced currents as expanding and contracting 

 stimuli. Under these circumstances he observed that the original pro- 

 cesses did not reappear in every case. He finally concluded that the 

 pigment in general follows fixed processes but that it is not forced 

 to do so, for, under the influence of the galvanic current, processes 

 appear in places where previously none had been visible. 



There is a serious objection to this conclusion. If the pigment 

 does not always reappear in the old processes, there is no proof 

 whatever that what Winkler regarded as new processes brought about 

 by the galvanic current, were not actually old ones in which the 

 granules had simply failed to appear at the previous observation. 



Fig. 1. A group of melanophores which have been 

 expanded in a 0.1 molecular sodium chloride solution. 

 (Obj. 8 nun Zeiss Apochrom., Oc. 6 Zeiss Comp ) 



