948 



SCIENCE 



[N. S. Vol. XXXIX. No. 1017 



Opinion conceming the lipoid theory is 

 divided among those who deny the truth of 

 both first and second statements; those who 

 admit the first but not the second and those 

 who accept the theory in its entirety. 



The acids form a group of substances of 

 particular interest in this connection in that 

 they are bodies widely different in chemical 

 composition and physical properties — lipoid 

 solubility, degree of dissociation, surface ten- 

 sion — yet the entrance of each into a living 

 cell may be detected by the same method — • 

 color change of a suitable indicator within. 



It is impossible to stain living cells with 

 dyes which will serve as indicators for acid, 

 as I had previously done for alkalies,^ so that 

 recourse must be had to organisms with natu- 

 ral indicators. In plants the blue anthocyan 

 pigments of petals are not sensitive enough to 

 weak acids, such as acetic, to warrant their 

 use. In animals despite the number and the 

 variety in color of pigmented forms, indicators 

 are very rare. 



Last winter while a member of the Great 



Barrier Eeef Expedition of the Carnegie Insti- 

 tution at Washington, I discovered a Holo- 

 thurian, Stichopus ananas, the " prickly fish " 

 of the Beche de Mer industry, whose viscera 

 contain a purple water-soluble pigment turn- 

 ing red-orange in a concentration of acid 

 between m/1,000 — m/500. The chemical com- 

 position of the pigment is unknown, but it 

 appears related to the antedonin described by 

 Moseley^ from crinoids and a deep-sea Holo- 

 thurian. The purple color is contained in sacs 

 or bodies of unknown nature thickly scattered 

 just under the epithelium covering the vari- 

 ous viscera, and is especially abundant in the 

 testes and ovaries, although not in the sperm 

 and egg cells themselves. It is of impor- 

 tance to note that the pigment is contained in 

 or surrounded by living cells and death of the 

 tissue results in a rapid diffusion of the purple 

 from the cells as in the case of so many other 

 pigments. Acid diffusing toward the indi- 

 cator must therefore pass through the layer 

 of living epithelial cells. 



A study of the penetration times of a large 



1 Jour. Exp. Zool, Vol. 10, 1910. 



2 Quart. Jour. Microscop. Science, Vol. 17, 1877. 



3 Cone, which just kills in 20 hours. 



* Insol. in xylol from n/100 cone in water but 

 slightly sol. from «./10 cone Eemaining acids 

 insol. from n/10 cone, in water. 



