CHEMICAL AGENTS ON CHROMATOPHORES 151 



experiments performed. If an intense stream of oxygen was 

 bubbled at the same time with the carbon dioxide, the pigment 

 cells remained expanded. The proportion of the two gases which 

 maintained the expansion of the melanophores was not de- 

 termined. Briefly summarized the results prove that carbon 

 dioxide produces a contraction of the pigment cells of trout 

 embryos. The presence of oxygen antagonized the action of the 

 carbon dioxide. 



Effects of distilled water 



The first experiments that were performed were to determine 

 the effect of distilled water on the pigment cells of trout embryos. 

 The normally expanded pigment cells contracted in ten to twelve 

 minutes and the fish died usually in about twenty minutes- 

 differing somewhat with the individual lots of fish. After an in- 

 terval of ten to thirty minutes, following the initial contrac- 

 tion, the pigment cells began to expand. This secondary ex- 

 pansion of the melanophores in no way equaled the normal ex- 

 panded condition. The processes of the cells were short and 

 blunt. This expanded condition lasted for a short period; then 

 the walls of the melanophores began to break down and the cell 

 contents, viz., the pigment granules migrated into the inter- 

 spaces of the epidermal layer. Often the pigment cells disinte- 

 grated without a previous expansion. Spaeth ('13) obtained 

 essentially the same results with isolated scales of Fundulus in 

 which the chromatophores (1) expanded, (2) contracted, (3) 

 expanded a second time with a final degeneration. He did not 

 try oxygenated distilled water. If 2 cc. of boiled tap water were 

 added to 8 cc. of distilled water the results were the same. 

 Then boiled tap water was tried and the pigment cells con- 

 tracted in fourteen and twenty-two minutes. In distilled and 

 boiled tap water through which oxygen had been bubbled the 

 melanophores remained expanded and the fish lived indefinitely. 

 The conclusion was obvious. It was oxygen want and not the 

 absence of salts in the distilled water that caused the contrac- 

 tion of the pigment cells and the death of the fish. 



