CHEMICAL AGENTS ON CHROMATOPHORES 167 



centration there was no primary stimulating period observed. 

 If it is to be fomid, it may be so short as to be very easily over- 

 looked. Alcohol in large amounts decreased the rate of contrac- 

 tion in the gastrocnemius frog's muscle, Lee and Salant ('02). 

 Romanes ('77) found that strong solutions of ethyl alcohol pro- 

 duced increased and spasmodic contraction of the medusa bells 

 of Sarsia (sp.) and Tiaropsis (sp.). These were followed by a 

 depression. 



Lee ('02) observed that in solutions of ethyl alcohol of a greater 

 concentration than 2 per cent the contractions of the bell of the 

 medusa, Gonionema, were much reduced in volume and in 

 number. Dogiel ('77) has shown a depression in the heart 

 rhythm of Corethra plumicornis. Vernon ('10) observed that 

 large doses of ethyl alcohol depressed the rate and volume of 

 the contraction of a turtle's heart (Emys). 



3. Propyl alcohol. Weak solutions of propyl alcohol 0.01 per 

 cent to 0.04 per cent did not effect the melanophores. In a 0.06 

 per cent there was a noticeable contraction of the pigment cells. 

 Solutions of 0.08 per cent to 0.125 per cent produced a rapid and 

 complete contraction. In 0.7 per cent to 1.3 per cent the contrac- 

 tion was only temporary, and was followed by an immediate 

 relaxation of the pigment cells. A 1.5 per cent to 2 per cent 

 produced no visible change in the expanded melanophores, and 

 when embryos with contracted melanophores were exposed to 

 the solution the melanophores expanded. In these concentra- 

 tions there was observed a marked disintegration (cytolysis) 

 of the cells. Higher concentrations (2.5. per cent to 4 per cent) 

 killed the embryos without inducing any change in the expanded 

 pigment cells. Contracted cells exposed to these solutions ex- 

 panded instantaneously and after this response gave no reactions 

 to other stimuli. 



It is obvious from these results that the stimulation of the 

 pigment cells by propyl alcohol begins in solutions of lower con- 

 centrations than it does in ethyl and methyl alcohol. It will be 

 seen that my results for methyl, ethyl, and propyl alcohols are 

 in perfect agreement with the results on the toxicity of the 

 above alcohols of other investigators. 



