146 



Papers from the Department of Marine Biology. 



aceto-carmine show regular epithelial nuclei and just below them the 

 pigment bodies which have no special nuclei connected with them. 

 Whatever their nature, acid must diffuse through an epithelium of 

 living cells to reach them. So long as the cells are living the pigment 

 remains in them, but if killed by heat or distilled water or chloroform- 

 saturated sea-water or acid or alkali, the pigment passes out, i. e., they 

 cytolyse and, as in so many other pigment-containing cells, the coloring 

 matter diffuses away. 



The chemical nature of the pigment is unknown. It is water soluble 

 and fairly unstable, decomposing into brownish compounds at 100 C. 

 If dissolved in sea-water and HC1 is slowly added, it changes in color 

 from dark red to orange when the concentration of acid becomes 

 ft/1000 to n/500. The color change is very nearly but not quite as 

 marked in a weak acid like butyric. On the addition of alkali the color 

 becomes purple. Moseley 1 in 1877 described a similar if not identical 

 pigment from crinoids dredged in the channel between Cape York and 

 Albany Island, Australia, and also from a deep-sea holothurian of 

 the South Indian Ocean. He called the pigment antedonin and I 

 shall adopt the same name. The echinochrome of MacMunn 2 and 

 McClendon 3 is no doubt a closely related pigment. 



TABLE 1. Temperature about 28 C. 



In the following experiments small pieces of the branched filamentous 

 testis were used. Acid was added to a neutral artificial sea-water of the 

 following composition, m/2 (100 NaCl+2.2 KCl+2CaCl 2 -flOMgCl 2 ), 

 until the proper concentration of acid was obtained. Oxalic acid pre- 

 cipitates the Ca so that this acid was added to m/2 NaCl. 



A study was first made of the penetration times of a weak (butyric) 

 and a strong (HC1) acid in different concentrations into living and dead 

 tissue. The results are given in table 1. The tissue was killed by 

 half-minute immersion in chloroform-saturated sea-water. Under 

 these conditions the pigment begins to diffuse out of the cells, but 

 in each case the acid penetrates before the diffusion is nearly complete. 



It will be noted that the living tissue is decidedly resistant as com- 

 pared with the dead, and that the resistance varies with the acid and 

 with the concentration of acid. Note that butyric acid in n/20 con- 



'Quart. Journ. Micros. Soc., 17, p. 5, 1877. 



2 Quart. Journ. Micros. Soc., 25, p. 469, 1885; 30, p. 51, 1889. 



Mourn. Biol. Chem. 11, p. 436, 1912. 



