1914] Ross Alken Gortner and Arthur M. Banta 3^5 



that the liquid was almost solidified and poured like a thin jelly. 

 In such a sol. the larvae remain suspended, being unable to swim. 

 Such an infection may result within 1-2 days. In other instances 

 the tyrosin sol. becomes a bright pink and later deposits black humin. 

 In such instances the bacterial infection probably secreted tyrosinase. 

 No effort has been made to identify any of the bacteria concerned 

 in these phenomena. We feel, therefore, some hesitancy in ascrib- 

 ing any definite toxic properties to tyrosin itself, although in a 

 saturated sol. it may show some slight toxicity to the eggs which we 

 have used. In like manner our results regarding the question of 

 pigmentation are not as satisfactory as we could wish. A number 

 of our experiments gave results that were not different from those 

 for the control material, while a few of the experiments produced 

 animals with less pigment, and developing less rapidly, than the 

 control. We have come to regard the negative outcome of these 

 experiments as arising from bacterial infection. 



The work on tyrosin embraced series of all of the amphibian 

 eggs with which we have worked in other experiments. Since the 

 course of pigmentation can be followed best in the larvae of Spe- 

 lerpes, and since no noteworthy results aside from pigmentation 

 have developed, we shall confine our details to the experiments in- 

 volving Spelerpes. 



There were 41 experiments with Spelerpes in tyrosin sol., each 

 experiment involving many embryos. Twenty experiments showed 

 no effect of the treatment; 11 of these 20 had been subjected to a 

 conc. of less than 0.008 percent and most of the remaining 9 experi- 

 ments had been influenced by the bacterial infections or had at first 

 shown some effect of the treatment and had later " reverted." 



Twenty-one experiments, comprising 220 individuals, were pro- 

 foundly influenced by the treatment and became "good" or "typ- 

 ical " tyrosin types. The tyrosin influence is shown by ( i ) the more 

 rapid appearance of pigment in the individuals in tyrosin sol. as 

 contrasted with the controls; (2) the extremely small size and 

 later the entire absence of pigmentless Spots in the larvae, the areas 

 where Spots are normally visible being filled with dense black pig- 

 ment;^ and (3) the dense dull black color of the larvae compared 



3 From this Observation it would seem probable that the pigment pattern, at 

 least in so far as it relates to the presence of Spots without the melanin, is formed 



