CILIARY ACTIVITY 39 



specific action of the added substance in either direction can 

 be conveniently observed. He recommends the following 

 formula for Fundulus : 6 vols. N/io NaCl, i vol. N/ 10 KCl, 

 0*35 vol. N/io CaClg. 



The most remarkable result which emerges in this con- 

 nection from Spaeth's experiments is the effect of barium salts, 

 which, as is well known, exercise a very characteristic excitatory 

 action upon true contractile tissues. After treatment of scales 

 for ten minutes in N/io BaCl2 no sign of recovery may appear 

 for as much as half an hour, during which the melanophores 

 remain completely contracted. After this period of quiescence, 

 the melanophores in the periphery of the scale abruptly expand 





Fig. 14. — Melanophores of Fundulus (Spaeth). 



Effect of adrenaline {a) on the partially contracted pigmentary effectors (b) ; 

 effect of adrenaline after previous immersion in ergotoxine (c). 



and contract almost at once. After a brief interval a second 

 expansion wave appears at the periphery, and melanophores 

 lying nearer the centre begin to behave in a similar manner. 

 This time, however, the peripheral melanophores expand more 

 completely. Eventually after about an hour the wave of 

 rhythmic expansion and contraction extends to the centre of 

 the scale so as to include all the melanophores, which pulsate 

 between the extremes of contraction and complete expansion. 

 This pulsation may continue for several hours. 



The Crustacean chromatophore consists essentially of a 

 centre, branches radiating therefrom in a luxuriantly ramifying 

 system. In the aduh forms of most Crustacea which have been 



