208 PROF. HUXLEY, ON SOME ORGANISMS FROM GREAT 



place of the intermediate substance. I do not wish to imply, 

 however, that the intermediate substance is something totally 

 distinct from the upper and lower plates. One would naturally 

 expect to find protoplasm between the two plates ; and the 

 granular asjiect which the intermediate substance frequently 

 possesses is such as a layer of protoplasm might assume. But 

 I have not been able to satisfy myself completely of the pre- 

 sence of a layer of this kind, or to make sure that the inter- 

 mediate substance has other than an optical existence. 



From their double-cup shape I propose to call the cocco- 

 liths of this forin Cyatholithi. They are stained, but not very 

 strongly, by iodine, which chiefly affects tl^e intermediate 

 substance. Strong acids dissolve them at once, and leave no 

 trace behind ; but by very weak acetic acid the calcareous 

 matter which they contain is gradually dissolved, the central 

 corpuscle rapidly loses its strongly refracting character, and 

 nothing remains but an extremely delicate, finely granulated, 

 membranous framework of the same size as the cyatholith. 



Alkalies, even tolerably strong solution of caustic soda, affect 

 these bodies but slowly. If very strong solutions of caustic 

 soda or potash are employed, especially if aided by heat, 

 the cyatholiths, like the discoliths, are completely destroyed, 

 their carbonate of lime being dissolved out, and afterwards 

 deposited usually in hexagonal plates, but sometimes in 

 globules and dumb-bells. 



The Cyatholithi are traceable from the full size just described, 

 the largest of which are about -piJ^-uth of an inch long, down 

 to a diameter of g ^'o „ th of an inch. Their structure remains 

 substantially the same, but those of -j-,jV(yth of an inch in 

 diameter and below it are always circular instead of oval ; 

 the central corpuscle, instead of being oval, is circular, and 

 the granular zone becomes very delicate. In the smallest 

 the upper plate is a flat disc, and the lower is but very slightly 

 convex (fig. 1 /). I am not sure that in these very small 

 cyatholiths any intermediate substance exists, apart from the 

 under or inner surface of the upper disc. When their flat 

 sides are turned to the eye, these young cyatholiths are ex- 

 traordinarily like nucleated cells ; and it is only by carefully 

 studying side views, when the small cyatholiths remind one 

 of minute shirt-studs, that one acquires an insight into their 

 real nature. The central corpuscles in these smallest cyatho- 

 liths are often less than Tnnhrdth of an inch in diameter, and 

 are not distinguishable optically from some of the granules of 

 the granule-heaps. 



The coccospheres occur very sparingly in proportion to the 

 coccoliths. At a rough guess, I should say that there is not 



