•2G GUIDE TO THE FOSSIL INVERTEBRATE ANIMALS. 
Gallery X. 
Class RADIOLARIA. 
'Pile central mass of protoplasm with the nucleus is 
surrounded hy a horny membrane, forming a capsule. 'Phis, 
in its simplest form, is spherical, and scattered evenly over 
its surface are numerous pores through which the protoplasm 
within it communicates with that outside it. In a higher 
stage the pores are grouped into several areas, but these in 
their turn are evenly distributed, so that there is still no 
definite axi.s. All these constitute the Porulosa of Haeckel. 
Fig. 6. — Radiolaria, Recent and Fossil, a, a living Radiolarian of the 
Order Nassellaria, Cyrtocalpis urccolus. Within the siliceous test is 
seen the central capsule, from the lower part of which the pseudopodia 
stream out through the mouth and lower meshes of the test. In the 
upper half is the large nucleus, on each side of which is an oil globule. 
The lighter round bodies are yellow algee. Enlarged 200 diameters. 
(After Haeckel, 1887.) b-e are fossil Radiolaria, b, c, and d being of 
Carboniferous age, and e being Silurian, b and e are examples of 
Spumellaria Sphaeroidea ; c of Spumellaria Discoidea ; and d of 
Nasselaria Cyrtoidea. All greatly magnified. (After Riist.) 
In tlie Other Radiolaria, which Haeckel names Osculosa, tlie 
pores are concentrated in a basal region called the osculum ; 
thus tlie capsule has a central a.xis with a basal and an apical 
pole ; smaller oscula may occur near the latter. In each of 
these divisions a skeleton may be developed, either of pure 
silica or of other substance. 
On these bases the Radiolaria are divided by Haeckel 
into four Orders: 1. Spumellaria: Porulosa, with ])ores 
scattered; skeleton of .solid silica. 2. Acantharia: Poru- 
