200 REYNOLD A. SPAETH 



A direct response to light has not thus far been demonstrated 

 in the melanophores of reptiles, though as Fuchs (loc. cit.) has 

 emphasized, it will in all probability be found to exist. 



We may now summarize the foregoing observations as fol- 

 lows; 1) in certain species of fish and amphibians the sphincter 

 pupillae contracts in response to direct stimulation by light; 2) 

 in certain other species of fish and amphibians the melanophores 

 also respond to direct stimulation by light by contracting. 



///. Effect of Electrical Stimulation 



Induction currents of sufficient intensity and duration produce 

 contractions in smooth muscle. Such contractions may be seen 

 in strips of frog's stomach prepared according to Meigs ('12), or 

 in preparations of the digestive tube of several species of tele- 

 osts.^ Beer ('94, '98) observed that the sphincter pupillae of the 

 eel and the frog (Rana) contracted w^hen stimulated electrically. 

 The radial muscles of the chromatophores of cephalopods also 

 respond to electrical stimulation by contracting (Briicke '52, 

 Keller '73, Fredericq '78, Klemensiewicz '78, Pouchet '76, Kruken- 

 berg '80, Phisalix '92, Steinach '01, Hofman '07, '10, and Fuchs 

 '10). Klemensiewicz (loc. cit.) records similar contractions in 

 isolated pieces of the skin of Loligo. 



Lode (loc. cit.) first showed that in excised pieces of the skin 

 of the trout the melanophores contracted upon being stimulated 

 by an induction current. In my own experiments with Fundu- 

 lus the melanophores invariably contracted, reversibly, when 

 proper strength and duration of the current and salt concentra- 

 tion of the mounting medium were selected. 



Winkler ('10) found that the melanophores of Rana esculenta 

 and Hyla arborea contracted when directly stimulated by an 

 induction current. Laurens (loc. cit.) has recently verified this 

 observation in large larvae of Amblystoma opacum. He finds 

 also that: ''When various portions of the body are cut out and 

 directly stimulated either with the central nervous system in- 



' Unpublished observations made upon the stomach muscle of Stenotomus, 

 Tautoga, Centropristes and Fundulus. 



