344 Mr. E. H. L. Schwarz on Coccoliths. 



The discoliths seem to be imbedded in a common mem- 

 brane, for they cohere in a mass for some time — in fact till they 

 are mature, or nearly so — and then they constitute what is 

 known as coccospheres, which have all the appearance of 

 spheres ; but when they are lifted on to their side they are 

 seen to be really flat, or, rather, halves of hollow spheres. 

 At first 1 took both the cyatholiths and coccospheres to be 

 actually spheres ; but on agitating the water on the slide 

 containing them I noticed, that, while some readily followed 

 the flow of the water, others remained stolidly fixed and 

 refused to move even when great masses of ddbris knocked 

 against them ; but suddenly, when the motion became too 

 violent, they gently turned on their sides and revealed the 

 hollowness of their nature. In the first instance they were, of 

 course, resting on their convex surfaces, but when they refused 

 to move they were with their concave surfaces downward. 

 Sollas {Joe. cit.) has figured these cyatholiths in the Cam- 

 bridge greensand as " coccospheres, covered loosely with the 

 oval form of the coccolith." Some of the cyatholiths seem to 

 have grown their larger cup too far forward, and the pro- 

 jecting part has then broken off, and appears surrounding the 

 cyatholith like a Saturn's ring (figs. 13, 14, 15) ; by carefully 

 agitating the water the ring may be made to slip on to its 

 proper place and off again. 



The dividing discoliths here described were seen through 

 the transparent calcite of the cup. To make sure that these 

 really were discoliths within the cyatholith I ran in a little 

 weak acetic acid on the slide (working with a £-inch objec- 

 tive without a cover-glass) ; the cups became dissolved and 

 the conjoined discoliths set free, when there was absolutely no 

 mistaking the form. On running in a little magenta the 

 outline of the cup reappeared, so that they are in all proba- 

 bility formed of a framework of horny material filled in with 

 calcium carbonate. A very curious fact is that, while the two 

 cups of the cyatholith dissolve freely in weak acid, the disco- 

 liths require fairly strong acid before they will disappear ; 

 and, comparing the rate of dissolution of both with that of a 

 Rotalia in a washing containing all three from the gauit, the 

 cups went at about the same rate as the foraminifer, but the 

 discoliths remained long after the latter had disappeared. 

 Hence I am inclined to think that the discoliths are largely 

 composed of calcium phosphate, a view which 1 was led to 

 entertain from the fact that the phosphatic chalk of Taplow 

 contains the discoliths (with few cyatholiths) in vast quantities. 



Wallich considered the coccospheres to be embryonic fora- 



