PHYSIOLOGY OF CHROMATOPHORES OF FISHES 539 



11.42 A.M. All the melanophores in the mixture were still fully expanded 



and all those in the distilled water were degenerating. 

 12.30 P.M. The mixture showed the melanophores still expanded. 

 1.20 P.M. The melanophores were contracted but not degenerating 



in the mixture. 

 3.25 P.M. The melanophores in the mixture were half expanded but 

 there was no sign of cytolysis. T. = 26°C. 



The following two experiments show that even at a dilution of 

 1 part sea-water to 50 of distilled water (1) the irritability is 

 maintained longer than in distilled water and (2) that the mix- 

 ture shows a distinct protective action against cytolysis. 



August 23, 1912 



8.54 A.M. Scales from an 8 cm. female were immersed in 8 cc. of dis- 



tilled water and 8 cc. of 1 part sea-: 50 distilled water, 

 respectively. 



9.04 A.M. Both sets were contracted. 



9.20 A.M. The melanophores of every scale in the mixture responded 

 to a 1 per cent atropine sulphate stimulus-^ and none were 

 relaxed. All but one scale in distilled water had relaxed 

 and degenerating melanophores and failed to respond to 

 the atropine sulphate stimulus. High power showed 

 empty processes in the melanophores of the mixture ex- 

 actly as in distilled water (fig. 6, pi. 1). The contraction 

 here was probably due to the dilution — the characteristic 

 hypotonic effect. T. = 25.5°C. 



. August 22, 1912 



4.55 P.M. Scales from an 8 cm. female were placed in 8 cc. of distilled 



water and 8 cc. of 1 part sea-: 50 distilled water respec- 

 tively. No distinct difference was observable at this di-i 

 lution between the contraction time of the mixture and 

 that in distilled water. 

 5.18 P.M. The relaxation was very distinct in the melanophores of 

 the distilled water set but not in those in the mixture. 

 All scales in the distilled water were more yellow to the 

 naked eye than those of the mixture (expanded xantho- 

 • phores). T.= 26°C. 



The most striking fact about these trials "with dilute sea-water 

 is brought out in the experiment of August 22 in which the dilu- 



= A 1 per cent solution of atropine sulphate causes a rapid expansion of the 

 melanophores which is irreversible by the contracting salts (vide infra). Fail- 

 ure to respond to this stimulus was consid ered a criterion for the loss of irritability. 



