574 R. A. SPAETH 



The anion sequence (p. 547 and pis. 2 and 3) is the familiar 

 one of Hofmeister ('91), Pauli ('99), Schwarz ('07), Port ('10) 

 and others (Hober, '11, pp. 353-354, 409, 399). 



Overton ('04) found that the chlorides of the alkalies preserved 

 the irritability of fresh frogs' muscle in the cation order 



Na >Li >Cs >NH4 >Rb >K 



With the doubtful exception of Cs+ and Rb+ this is precisely 

 the order in which the melanophores of Fundulus retain their 

 irritability in the chlorides of these metals. Hober ('11, chapt. 10) 

 emphasizes the correlation which this series has brought out be- 

 tween irritability and the state of colloidal aggregation. 



In addition to the foregoing experiments upon F. heteroclitus 

 the chromatophores of several other species of teleost fishes were 

 tested in solutions of NaCl and KCl.'-* Although none of these 

 species proved so favorab e as F. heteroclitus, the results showed 

 that the physiological responses of the melanophores are essen- 

 tially the same in all the forms examined. It therefore seems 

 highly probable that the melanophores of all color-changing tele- 

 osts are sensitive to direct physiological stimuli of the type de- 

 scribed in this paper. 



The results of these experiments upon the responses of the 

 chromatophores of F. heteroclitus may be briefly summarized as 

 follows : 



1 . The two types of chromatophores (melanophores and xan- 

 thophores) are normally under the control of the sympathetic 

 nervous system. 



2, When scales, bearing the superficial layer of chromato- 

 phores, are removed from the fish to sea-water, there is prac- 

 tically no change in the position of the melanophore pigment 

 (p. 533). Distilled water causes a contraction, dilute sea- water 



* Such experiments were carried out upon the following species — F. majalis 

 Walbaum (May Fish) ; Cyprinodon variegaius Lacepede (Pursy Minnow) ; Palin- 

 urichthys perciformis Mitchill (Black Rudderfish) ; Morone americana Gnielin 

 {White Perch) ; Centroprisles strialus Lin., (Black fish); Tautogolahrus adspersus 

 Walbaum (Gunner); Tauioga onilis Lin., (Tautog); Eupomotis gibbosus Lin., 

 (Freshwater Sunfish). , 



