50 The Ohio Naturalist. [Vol. XIII, No. 3, 



By macerating larva which were about to begin pigmentation 

 and adding tyrosin to the aqueous extract of the crushed larvae, 

 we observed the color changes which are characteristic of tyro- 

 sinase. We have also satisfied ourselves that the onset of pig- 

 mentation in the Spelerpes larvae is due to the beginning of chro- 

 mogen secretion, the tyrosinase having been already present for 

 some time. 



Experimental. 



Our experimental data groups itself under four heads: (1), 

 Experiments with Tyrosin; (2), Experiments with Orcinol, (3. 5. 

 di -hydroxy toluene); (3), Experiments with Resorcinol, (m. di-hy- 

 droxy benzene) and (4), Experiments with Phloroglucinol, (sym. 

 tri-hydroxy benzene). 



Experiments with Tyrosin. 



This series comprised 41 experiments (not including an equal 

 number of checks) and a total of 428 individuals. The checks 

 in every case came from the same bunch of eggs and were kept 

 under the same conditions as the tyrosin-treated lot with the 

 exception that no drugs were used. What is true of the tyrosin 

 checks is also true in the checks of all the subsequent experiments. 

 Owing to the slight solubility of tyrosin (one part in 2454 parts of 

 water at 2U°) it was impossible to test the effect of high concen- 

 tration. Twenty experiments, comprising 208 individuals showed 

 no marked effect of the tyrosin, /. e. they were usually indisting- 

 uishable from the corresponding checks. We find however that 

 in 1 1 of these experiments the tyrosin was of a lower concentration 

 than 0.008% and below this concentration we have succeeded in 

 but one case (0.006%) in producing an effect and in this one case 

 the larVcB "reverted " to nonnal after 28 days. Six of the remain- 

 ing nine experiments which showed no effect are shown by our 

 records to have been "poisoned", either by confinement in too 

 limited quarters or by bacterial infection. The checks of those 

 which were confined in too small dishes (small stcnder dishes) 

 showed the same abnormal traits that were observed in the 

 treated material. Of the remaining three experiments which 

 failed to show a marked effect, two were in tyrosin of 0.025% 

 concentration and the remaining lot in 0.010% tyrosin. The 

 former showed some influence for a time but later "reverted." 

 The other showed no influence. 



Twenty-one experiments, comprising 220 individuals were 

 profoundly influenced by the tyrosin treatment and bccaine 

 "good" or "typical" tyrosin types. The tyrosin influence is 

 shown by; (1), The more rapid appearance of ])igment in the 

 treated lot as contrasted with their checks; (2), The extremely 

 small size and later the entire absence of pignicntless spots in 

 the larvae, the spaces where spots arc nonnally visible being filled 



