50 
The Ohio Naturalist. 
[Vol. XIII, No. 3, 
By macerating larvae 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 Oreinol, (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 tvrosin-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 20°) it was impossible to test the effect of high concen¬ 
tration. Twenty experiments, comprising 20S individuals showed 
no marked effect of the tyrosin, i. e. they were usually indisting¬ 
uishable from the corresponding checks. We find however that 
in 11 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 larvae “reverted” to normal 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 stender 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 became 
“good” or “typical” tyrosin types. The tyrosin influence is 
shown by; (1), The more rapid appearance of pigment in the 
treated lot as contrasted with their checks; (2), The extremely 
small size and later the entire absence of pigmentless spots in 
the larvae, the spaces where spots are normally visible being filled 
