S66Toxicity of Dilute Solutions of Phenolic Compounds [April-July. 



with which the control animals often appear comparatively light. 

 There is no mistaking the "tyrosin type," for an inexperienced 

 person will always pick them out as the darkest individuals in a 

 series. 



Experiments with /»-hydroxy-phenyl Ethanol (Tyrosol). 

 Tyrosol was prepared from tyrosin by the action of yeast (Ehrlich, 

 191 1). When treated with tyrosinase it was found that the typical 

 black color could not be obtained, only the soluble colors of the 

 System, tyrosin-tyrosinase, being produced, i. e., pink to rose to red, 

 Inasmuchas tyrosol differs from tyrosin only by an amino and a 

 carboxyl group attached to the a-carbon atom of the aliphatic chain, 

 it seems probable that the soluble colors produced by the action of 

 tyrosinase on tyrosin are the result of a quinone formation acting on 

 the /»-hydroxyl group, and that the production of the black humin 

 involves the aliphatic amino group. 



Since tyrosol is acted on by tyrosinase to produce a red color, 

 we thought the color of the larvae of Spelerpes might be influenced 

 by rearing them in sol. of tyrosol. Conc. of tyrosol varying from 

 O.I-0.0125 percent were employed. The higher conc, 0.1-0.05 

 percent, proved to be quite toxic, causing the death of the larvae 

 within 15 days. The retardation of growth was very marked as 

 was also the retardation of pigmentation. Whether there was a 

 greater retardation of pigment development than could be explained 

 by the retardation in growth and general body development we are 

 unwilling to State without the aid of larger series of material. 

 Those animals which were placed in sol. of tyrosol of 0.025-0.0125 

 percent conc, showed retardation in general body development and 

 slowness in the development of the normal pigment pattern. How- 

 ever, after about a month in the sol., they reached a stage where 

 they were " indistinguishable from the controls " and shortly after 

 this time they were discarded. 



by a localized secretion of the chromogen while the oxidizing enzyme is distributed 

 through the skin tissues of the entire body surface. Such a hypothesis will serve 

 to explain the absence of spots in the larvae treated with tyrosin, which would 

 take the place of the chromogen. From the previous workof one of us [Gortner, 

 191 1 (c)], it seems probable that this is the case in the development of the color 

 pattern of LepHnotarsa decetnlineata. 



