CORAL REEFS OF TORRES STRAITS 229 



with great rapidity when disturbed. They are often called "brittle 

 stars," for if one seizes an arm it is promptly cast off, permitting the 

 major portion of the animal to escape. Their beautiful sculpturing, rich 

 colors, and the ornate patterns of their disks were admirably figured in 

 color by Mr. E. M. Grosse, who executed more than 100 beautiful draw- 

 ings which will serve to illustrate Dr. Clark's purposed paper upon the 

 Echinoderms of Torres Straits. Indeed, Dr. Clark aptly called the region 

 " a paradise for echinoderms," and it appears to be the richest known lo- 

 cality in the world for shallow-water forms of these animals, for Dr. 

 Clark found 51 species at Maer Island alone, and in addition, he collected 

 26 others at Badu, Darnley and Thursday Islands; making 177 from 

 Torres Straits. Thus his collection is a notable addition to that of the 

 Museum of Comparative Zoology at Harvard, which was probably al- 

 ready the greatest gathering of specimens of echinoderms in the world. 

 In almost every instance Mr. Grosse's figure is the only colored drawing 

 of these Torres Straits species, and thus Dr. Clark's paper will be a 

 classic upon the subject of tropical Pacific echinoderms. 



117 species had been previously recorded from Torres Straits, 

 and of these, Dr! Clark found only 42, but in addition he found at 

 least 45 not previously known to science, so that at present fully 250 

 echinoderms are known from this extraordinary region. 



As is well known to physiologists, the important subject of the pene- 

 tration of living cells by alkalies has for several years engaged the atten- 

 tion of Dr. E. Newton Harvey, of Princeton, and his results essentially 

 support Overton's lipoid theory, namely, that those substances which are 

 most readily dissolved in fat-solvents enter living cells most readily ; and 

 this leads one to suspect that the cell surface may be lipoid, or fat-like in 

 nature. 



Xo one had been able to test this hypothesis for acids, until Dr. Har- 

 vey discovered a holothurian at the Murray Islands, Stycopus ananas, 

 the intestines of which are purplish-red. If placed in acid, however, 

 they turn bright red, and in alkalies dark purple; and these changes 

 are reversible and may take place in weak acids or alkalies without kill- 

 ing the cells. Dr. Harvey used 24 different kinds of acids in dilute 

 solutions upon this animal and found that those which are most poison- 

 ous penetrate most rapidly, and all the acids penetrate about in the ratio 

 of their degree of toxicity. There is, on the other hand, no relation be- 

 tween the degree of dissociation of an acid and its rate of penetration 

 of the living cells ; and there is only a fair but by no means perfect 

 agreement between the rate of penetration and the solubility of an 

 acid in xylol. 



Overton's theory applies, however, with the majority of acids, but 

 the agreement is not perfect, and hence Harvey concludes that the power 

 of penetration of an acid depends not only on its lipoid solubility but 



