368 Dr. O. Schmidt on Coccoliths and Rhabdoliths. 



the central parts, the granide and the medullar disk, appears 

 undoubtedly from their arrangement and the connexion of the 

 other parts with them. The dorsal shield is nothing but a 

 covering piece, and, notwithstanding its extent, of subordinate 

 importance. In the globular and graiudar zone, however, I 

 see the reproductive apparatus. In favour of this there are 

 several reasons. So long as, like the previous observers, we 

 discovered in the granular zone only quite indefinite granula- 

 tions, the question as to the significance of this part of the 

 coccolith could hardly be raised ; but by the present inves- 

 tigation the granular zone must be placed in quite a different 

 light. That the formation of the coccoliths starts from cor- 

 puscles which vary in form and size exactly like the globular 

 and ellipsoidal portions of the granular zone, is easy to observe. 

 Exactly the same scope that we see in the foundations of the 

 coccoliths is repeated in the dimensions of the parts of the 

 granular zone, from the small globules like those we find in 

 coccoliths such as PI. XVI. fig. 15, to the large lenticular 

 bodies in fig. 1 1 . The former are isolated as central granules j 

 the latter appear as central granules with a medullar space. 

 An intermediate step is formed by the globule in PI. XVII. 

 figs. 1 and 3 ; and their perfect picture is the central glo- 

 bule in PI. XVI. fig. 3. The extraordinary variability of the 

 mature coccoliths will therefore be in accordance with an 

 equally wide scope in their foundations ; and the multifarious 

 forms of the coccolith-cycle, still by no means exhausted by 

 Hackel and myself, prove (notwithstanding the identity of 

 discoliths and cyatholiths) that we have to do with nothing 

 less than a fixed species. But when we have once accepted 

 the notion that the corpuscles of the granular zone are the 

 spores of the coccoliths, the appearance of many coccoliths is 

 explained by it, as, for example, PL XVII. figs. 6, 10, and 14. 

 In fact we often see, instead of the granular zone, which is 

 elsewhere so distinct, an irregular ring or an empty disk-margin. 

 For this I know no other explanation than that the granules 

 have fallen out, leaving behind them that margin belonging to 

 the medullar space from which the growth and production of the 

 corpuscles of the granular zone took place. It is certainly 

 remarkable that specimens such as PI. XVII. fig. 14 are rare ; 

 but they show quite evidently a retrogression and degradation, 

 which is expressed in the brittleness of the central disk and 

 the shrinking of the dorsal shield. It will be objected that 

 this is incompatible with the apparently uninterrupted accu- 

 mulation of the coccoliths. But in opposition to this it may 

 be said that the fossil coccoliths are still but very little inves- 

 tigated. The form with a finely granular zone (PI. XVI. 



