Jan., 1913.] Pigment Development in Spelerpes Larvae. 
53 
Experiments with Resorcinol. 
A total of 150 experiments, including 103 which had as their 
aim the test of the effect of varying length of immersion in the 
drug, were conducted using 636 larvae, not including checks in 
each series. We find that resorcinol is more potent than orcinol, 
not alone in being more toxic, but the type produced by it is, if 
possible, more definite. The same swellings of the serous cavities 
are produced if the eggs are treated before reaching the late neural 
groove. When treated before reaching the blastula, no larvas 
were hatched. 
When larvae which had the head strongly differentiated or 
were in any stage between this and a day or two after the begin¬ 
ning of pigmentation, were treated with resorcinol in sufficient 
concentration (0.020% to 0.025% and in one instance 0.05%) 
and for a sufficient length of time (4 to 10 or more days) they were 
highly modified and produced one of two types. Both types 
begin with a retardation of development and a great retardation 
of pigmentation. The first pigment appears in the eye and in a 
day or two a narrow V appears on the shoulders, followed 
a little later by a narrow line down the spine. This condition 
persists as long as the larvce remain in the resorcinol, but unfor¬ 
tunately the drug is so toxic that 15 to 18 days immersion invari¬ 
ably causes death. We have had many instances where the larvae 
which were treated with resorcinol appeared almost entirely 
devoid of pigment except for the dark eyes, when the correspond¬ 
ing checks were completely pigmented and the spots were fully 
developed. 
When the larvae are removed from the resorcinol solution after 
varying lengths of time we obtain the same two types referred to 
above. The more extreme type (See Fig. No. 1) resembles the 
“orcinol type” but is heavier, the “flippers” are more enlarged, 
and the pigment reticulation is very fine as contrasted with the 
coarse reticulations of the orcin type. This type persists for 60 to 
70 days when death by starvation ensues. 
The second type probably represents those individuals which 
have not been so profoundly modified. The body fonn is almost 
normal, the limbs and toes are well developed, but the spots are 
absent and the pigment pattern is very fine and dull in color. 
The majority of this type also die of starvation, and on Dec. 6— 
about 161 days from the beginning—we have only a very few 
individuals remaining. None of these have been “typical” but 
have been classed as “fair resorcin” or “somewhat modified” 
and all but two of these larvae still show modification. At this 
period of development, however, the checks have lost their charac¬ 
teristic markings so that a closer analysis is impossible. In 
nearly every instance in both the orcinol and resorcinol series, the 
surviving individuals are lighter than the checks. 
