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SCIENCE 



[N. S. Vol. XL. No. 1025 



strated, they should not be confused with the 

 true animal pigment. He accepts the theory 

 suggested by von Fiirth, that all pigments are 

 formed by the action of an oxidase of the 

 tyrosinase group on an oxidizable chromogen, 

 and demonstrates his claim by experiments 

 with meal worm and the cicada.^ In the 

 former he finds that the normal coloration 

 develops after the death of the larva, i. e., 

 after the secretion of the enzyme has ceased, 

 while in the latter life is necessary to produce 

 the normal coloration, although the enzyme 

 once formed does not depend upon life proc- 

 esses. Accordingly, the rise of the true 

 melanins is closely bound up with the enzymes 

 and demands a biological investigation as 

 well as a chemical, if such distinction is still 

 justifiable in the light of modern chemico- 

 physical interpretations of life phenomena. 



During twenty years of experimentation I 

 have found the oyster (Osircea Virginiana) 

 the most convenient and fruitful animal for 

 the investigation of the nature and origin of 

 pigments, because it can be easily handled and 

 the conditions of light, temperature, food 

 supply and pathological changes are readily 

 controlled. My earlier experiments which 

 were published from time to time in the Pro- 

 ceedings of the Academy of Natural Sciences 

 of Philadelphia, 1893, in the Bulletin of the 

 University of Pennsylvania, in the Annals and 

 Magazine of Natural History of London and 

 in the American Journal of Physiology, exclu- 

 sively dealt with the influence of light on 

 animal tissue under pathological conditions. 

 My latest experiments, permitted through the 

 courtesy of Dr. C. B. Davenport at the Cold 

 Spring Harbor Experiment Station, took into 

 consideration light, temperature, food supply 

 and the absence of pathological influences. 

 Several hundred oysters were opened without 

 injury to the adductor muscle or any other 

 part of the animal, except the shell, and 



1 "Studies on Melanin," I., Method of Isolation, 

 Jo^Lrnal of Biol. Chem., 1910, II., The Pigmenta- 

 tion of the Periodical Cicada, Journal of Biol. 

 Chem., 1911, in., "The Inhibitory Action of Cer- 

 tain Phenolic Substances upon Tyrosinase," Jour- 

 nal of Biel. Chem., 1911. 



placed on wire netting in a trough through 

 which sea water flowed with varying degrees 

 of velocity. Some of the oysters were placed 

 within the fraction of an inch of the water 

 surface, others at varying depths down to six 

 inches or more from the surface. Enough of 

 the left shell was removed to expose the 

 greater part of the left mantle, the peri- 

 cardium, the gills and the inner edge of the 

 right mantle. The experiments were carried 

 on from July 6 till August 15 at a time when 

 the sun's rays are most effective and in a 

 place exposed to the full sunlight during at 

 least eight hours of the day. Eighty per cent, 

 of all the oysters died after a few days of 

 exposure; the remainder gradually darkened 

 all over the exposed surface turning first light 

 brown and finally jet black, while the removed 

 shell was slowly regenerating along the broken 

 margin. The temperature of the water varied 

 on different days between 50 and YO degrees 

 Fahrenheit, with slight variations of several 

 degrees between the various depths. There 

 was also a difference in the quantity of the 

 excreta, being enormously large in the oysters 

 placed nearest the surface, showing a differ- 

 ence in the quantity of the food and in the 

 oxydation process. The latter also blackened 

 most rapidly, particularly along the gill bars 

 and over the tentacles of the mantle. All the 

 indications showed that the surviving oysters 

 would fully regenerate their shells and con- 

 tinue to live as though nothing abnormal had 

 occurred. In his experiments with the cicada 

 Dr. Gortner found that the insect just emerged 

 from the pupal shell and exposed to the action 

 of the air rapidly turned black without regard 

 to light, for several colorless adults which he 

 exposed to strong light, dim light, total dark- 

 ness and light which had passed through blue 

 glass, showed no apparent difference in the 

 rapidity of coloration nor in the final depth 

 of color. Nor did Victor Eaussek observe even 

 a trace of additional pigmentation when he 

 exposed oysters for many weeks to the direct 

 rays of the sun or a diminution of the normal 

 pigment when he placed them for several 

 weeks in darkness. In all my experiments the 

 phenomena of pigmentation and depigmenta* 



