REPORT ON THE RADIOLARIA. 723 



the bifid spines are so deeply cleft that they become forked. Much more interesting 

 and more varied than these different forms of the distal end are those of the apophyses 

 of the radial spines. 



The Apophyses of the Radial Spines, or their " lateral transverse processes," are of the 

 greatest importance for the morphological development of the whole subclass. Only in 

 sixteen among the sixty -five genera of ACANTHARIA are the apophyses perfectly wanting ; 

 in the other genera they determine in the first place their general character. In the 

 Acanthometra the apophyses remain perfectly free, whilst in the A c a n t h o- 

 p h r a c t a their meeting ends or branches compose the latticed shell. All differences in 

 form and shape of the apophyses can be reduced to only two primary modes ; either the 

 spine bears two opposite or four crossed apophyses ; correspondingly all Acantharia 

 apophysaria may be divided into two different main groups, the Zygapophysica (with 

 two opposite lateral processes) and the Staurapophysica (with four crossed lateral processes 

 opposite in pairs). Both groups have probably no direct phylogenetic connection, but 

 seem to be derived independently from different stocks, and produce different families. 

 The Zygapophysica are probably derived from Astrolonchida with two-edged spines 

 (Zygacantha], and from this group arise the Diporaspida, the ancestral group of the 

 majority ofAcanthophracta. On the other hand the Staurapophysica are probably 

 derived from Astrolonchida with four-edged spines (Acanthonia), and from this group 

 arise the Tessaraspida. The apophyses of the Acanthonida are partly simple, partly 

 branched or even latticed ; the apophyses of the Acanthophracta are never simple, 

 constantly branched and commonly latticed. 



The Malacoma (or the whole soft body of the ACANTHARIA as opposed to the skeleton) 

 exhibits some peculiarities which distinguish them from the other Eadiolaria, as well in 

 the structure of the central capsule and its nucleus as in that of the enveloping extra- 

 capsular body and the pseudopodia. 



The Central Capsule is constantly spherical in the far greater number of the ACAN- 

 THARIA, viz., in the following six families : Astrolophida, Chiastolida, Astrolonchida, 

 Dorataspida Sphserocapsida, and Phractopeltida. Among these six families the Astrolon 

 chida and Dorataspida are far greater and far richer in different forms than all the other 

 families. The central capsule becomes ellipsoidal or cylindrical, prolonged in one 

 axis, iu the three families, Amphilonchida, Belonapsida, and Diploconida ; it becomes 

 discoidal or lenticular, by the shortening of one axis, in two families, viz., in the Quadri- 

 lonchida and Hexalaspida. Finally, the peculiar family Litholophida is distinguished 

 by the conical form of its central capsule. 



The Membrane of the central capsule in all ACANTHARIA is simple, commonly thin, 

 sometimes very delicate ; in some species it seems to be developed late, just immediately 

 before the formation of the spores ; but in no species is it completely missing. The 

 membrane is constantly pierced by innumerable fine pores, for the emission of the 



