536 R. A. SPAETH 



sex and temperature are constant. These difficulties are ob- 

 viously eliminated at a stroke when scales from the same indi- 

 vidual are compared. 



Decapitation of a normal light fish is always followed by a 

 rapid darkening owing to the removal of the nervous inhibition 

 of the melanophores and their subsequent extreme expansion. 

 Obviously when a scale is removed from the living fish, the ner- 

 vous connections are severed and, unless there be some second- 

 ary inhibiting factor, an expansion of the melanophores should 

 follow exactly as in the decapitated fish. This is actually what 

 occurs in the case of distilled water, a uniform and synchronous 

 expansion of all the melanophores. Hence only the peripheral 

 contraction and the second semi-expanded state from which the 

 melanophores degenerate, can be considered as specific effects of 

 distilled water. This characteristic peripheral contraction is due 

 to the gradual advance of the diffusing fluid which seems to pen- 

 etrate most readily at the edge of the scale where epidermis and 

 derma have been torn from their original attachments. It 

 therefore seems highly probable that the epidermis is impermeable 

 to distilled water. 



Additional proof for this impermeability of the epidermis is 

 seen in the case of pithed and decapitated fish which lie in dis- 

 tilled water. Under these circumstances the melanophores re- 

 main expanded for hours. Their ultimate degeneration under 

 these conditions is the result of anemia and autolysis and not 

 of the cytolytic effect of distilled water. In certain of the ex- 

 periments with salt solutions this impermeability of the epider- 

 mis is brought out even more strikingly. 



The experiments of Garrey ('05) are of interest in this connec- 

 tion. In a number of fish of this species scales were scraped 

 from a considerable area of the body. These fish were then 

 divided into three lots — the first being returned to sea-water, 

 the second to distilled water and the third to a mixtiu-e of equal 

 parts of sea and distilled water. All fish of the first and second 

 lots died. At the end of four weeks 70 per cent of those in the 

 dilute sea-water were alive. Garrey attributes the toxic effects 

 of the sea-water and distilled water to changes in the osmotic 



