l^oToxicity of Dilute Solutions of Phenolic CompomidslApril-July. 



their shorter length, greater girth, absence of any conspicuous Spots, 

 development of heavy awkward " flippers " in place of delicate limbs 

 and toes, coarse reticulation of the pigment pattern, sluggish move- 

 ments and disability, or disinclination, to take food. This last trait 

 prevents our knowing how permanent this type may be, for they 

 gradually grow smaller and eventually die of starvation in an aver- 

 age of 8-9 weeks after hatching. 



It would thus appear that, although orcinol is very toxic in excess 

 of 0.025 percent conc, it is not nearly so toxic as is some other 

 substance [oxidation product ( ?)] formed by the action of light on 

 an orcinol Solution. The formation of this new Compound can be 

 easily observed by the development of a pink color, deepening to 

 red as the reaction progresses. In Solutions of 0.025 percent or 

 weaker the toxic effect, although still marked, is of much less in- 

 terest than the remarkable influence which the drug exerts upon the 

 course of development. Sol. of 0.005 P^r cent conc. showed but 

 little toxic effect w^hen kept in a dimly lighted room and had little 

 or no effect upon the course of development. 



Experiments with w-di-hydroxy benzene (Resorcinol). 

 A total of 150 experiments were made using eggs and embryos of 

 Spelerpes bilineatus. As with orcinol, w^e found that resorcinol is 

 much less toxic virhen the sol. is kept in the dark than when exposed 

 to the light A very dilute sol. of resorcinol (0.005 percent) be- 

 comes very toxic when placed for a time in bright light, the sol. 

 deepening in color from colorless to light yellow to brownish 

 orange. 



We find that resorcinol is more toxic than orcinol, but that 

 both have a similar influence on the course of development, the 

 " resorcinol type ", however, being perhaps still more definite than 

 the corresponding "orcinol type." The same swellings are pro- 

 duced when young embryos are placed in sol. of the drug. When 

 eggs are treated before reaching the blastula, no larvae are hatched. 



Perhaps the most noteworthy feature of the resorcinol experi- 

 ments is that dealing v/ith the Inhibition of pigmentation. When 

 larvae are treated with resorcinol sol. (0.02-0.05 percent) after the 

 head is well differentiated, up to within a day or two of the begin- 

 ning of pigmentation, and are kept in the sol. a sufiicient length of 



