THE RAY-STREAMERS. 67 
organisms develop in the formation of their skeletons such 
an amount of various fundamental forms, such geometrical 
recularity, and such elegant architecture. Most of the forms 
as yet discovered, I have given in the atlas accompanying 
my Monograph of the Radiolaria.”? Here I shall only 
give as an example the picture of one of the simplest 
forms, the Cyrtidosphera echinoides of Nice. The skeleton 
in this case consists only of a simple trelliced ball (s), with 
short radial spikes (a), which loosely surround the central 
capsule (c). Out of the mucous covering, enclosing the 
latter, radiate a great number of delicate little pseudopodia 
(p), which are partly drawn back underneath the shell, and 
fused into a lumpy mass of mucus. Between these are 
scattered a number of yellow cells (J). 
Most Acyttaria live only at the bottom of the sea, on stones 
and seaweeds, or creep about in sand and mud by means 
of their pseudopodia, but most Radiolaria swim on the 
surface of the sea by means of long pseudopodia extending in 
all directions. They live together there in immense numbers, 
but are mostly so small that they have been almost com- 
pletely overlooked, and have only become accurately known 
during the last fourteen years. Certain Radiolaria living 
in communities (Polycyttaria) form gelatinous lumps of some 
lines in diameter. On the other hand, most of those living 
isolated (Monocyttaria) are invisible to the naked eye; but 
still their petrified sells are found accumulated in such 
masses that in many places they form entire mountains; for 
example, the Nicobar Islands in the Indian Archipelago, and 
the Island of Barbadoes in the Antilles. 
As most readers are probably but Iittle acquainted 
with the eight classes of the Protista just mentioned, I shall 
