564 R. A. SPAETH 



contracted melanophores) into an open Syracuse glass in the air (any 

 mechanical stimulus due to this manipulation would have caused a 

 contraction). All the melanophores began expanding at once. After 

 six minutes, the expansion was well advanced. Forty minutes later 

 the scales in the air showed completely expanded melanophores and 

 the control set which had been attached to the hydrogen generator 

 when the first set was removed, showed a complete contraction. 



The hydrogen used in these experiments as in all others, was 

 obtained from the interaction of metallic (electrolytic) sheet 

 aluminum and a 20 per cent solution of chemically pure KOH 

 made up with distilled water. Before coming in contact with 

 the salt solution the gas was passed through two towers of moist 

 glass beads to prevent any possibility of a transfer of KOH. The 

 water in these towers was tested with phenolphthalin and the 

 salt-solution was similarly tested at the close of the experiment. 

 Neither the NaCl solution nor the water of the second tower gave 

 a hydroxy 1 test. 



The above experiment was repeated a number of times and, 

 with the exception of variations in the time of the response to 

 the absence of oxygen (for example, April 26, 1912; "melanophores 

 contracted in the hydrogen atmosphere in eighteen minutes") the 

 results were the same. In every case the complete elimination 

 of oxygen caused a contraction of the melanophores. 



Since the absence of oxygen can overcome the specific expand- 

 ing effect of a 0.1 M NaCl solution it seemed possible that mel- 

 anophores which had been contracted in a 0.1 M KCl solution 

 might be reciprocally expanded in an atmosphere of oxygen. 

 The results of such experiments were entirely negative. Other 

 experiments with mixtures of potassium and sodium salts in 

 which there was just enough potassium to keep the melanophores 

 contracted showed no expansion of the melanophores after long 

 exposures to an oxygen atmosphere. 



These last experunents suggest that possibly oxygen may act 

 merely in a passive manner and not as a specific expanding stim- 

 ulus in the same sense that NaCl, atropine sulphate, and niethyl- 

 ene blue cause an expansion of the melanophores. 



The results of these experiments show (1) that the melano«- 

 phores are unable to remain expanded in the absence of oxygen; 



