206 PROF. HUXLEY, ON SOME ORGANISMS FROM GREAT 



* 



oval or rounded figure (fig. 1 c). Some of the heaps attain 

 i_i_^th of an inch or more in diameter, while others have 

 not more than a third or a fourth of that size. The smallest 

 granules are rounded ; of the larger, many are biconcave 

 oval discs, others are rod-like,* the largest are irregular. 



. Solution of iodine stains the granules yellow, while it does 

 not affect the matrix. Dilute acetic acid rapidly dissolves 

 all but the finest and some of the coarsest granules, but appa- 

 rently has no eff'ect on the matrix. Moderately strong solution 

 of caustic soda causes the matrix to swell up. The granules 

 are little affected by weak alkalies, but are dissolved by strong 

 solutions of caustic soda or potash. * 



I have been unable to discover any nucleus in the midst of 

 the heaps of granules, and they exhibit no trace of a mem- 

 branous envelope. It occasionally happens that a granule- 

 heap contains nothing but granules (fig. 1 a), but, in the 

 majority of cases, more or fewer coccoliths lie upon, or in 

 the midst of, the granules. In the latter case the coccoliths 

 are almost always small and incompletely developed (fig. 

 \b,c). 



The coccoliths are exceedingly singvilar bodies. My own 

 account of them, qiioted above, is extremely imperfect, and 

 in some respects erroneous. And though Mr. Sorby's 

 description is a great improvement on mine, it leaves much 

 to be said. 



I find that two distinct kinds of bodies have been de- 

 scribed by myself and others under the name of coccoliths. 

 I shall term one kind DiscoUthus, and the other Cyatho- 

 lithus. 



The Discolithi (fig. 2) are oval discoidal bodies, with a 

 thick, strongly refracting rim, and a thinner central portion, 

 the greater part of Avhich is occupied by a slightly opaque, 

 as it were, cloud-like patch. The contour of this patch 

 corresponds with that of the inner edge of the rim, from 

 which it is separated by a transparent zone. In general, the 

 discoliths are slightly convex on one side, slightly concave on 

 the other, and the rim is raised into a prominent ridge on 

 the more convex side, so that an edge view exhibits the 

 appearance shown in fig. 2 d. 



The commonest size of these bodies is between xVo-otb and 

 ^-jjip-^th of an inch in long diameter; but they may be found, 

 on the one hand, rising to Ti^'Trnth of an inch in length, 

 (fig. 2/), and, on the other, sinking to -j-rJrTrrrth (fig. 2 a). 

 The last mentioned are hardly distinguishable ftom some of 



* Tlicse a])p;ireiit roils arc not merely cilu'e views of disks. 



