88 
Protozoa — 1 Radiolaria. 
Gallery, 
No. 10. 
Fossil 
Sponges. 
Table-cases, 
Nos. 11 to 15, 
ancl Wall- 
cases, 7 & 8. 
skeletons of siliceous sponges ; in many instances the flints are 
formed round the sponges, and when broken and their inner 
surfaces polished, the canals of the sponges are distinctly shown. 
Sponges of Tertiary age are rare, and are represented by 
the minute borings of the genus Gliona in molluscan shells. 
The Fossil Sponges occupy Table-cases Nos. 11-15, and 
Wall -cases Nos. 7 and 8. 
The Fossil Sponges have been most carefully described, 
catalogued, and copiously illustrated by Dr. G. J. Hinde, l.G.fe., 
and the work has been published by order of the Trustees. 
Sub-Kingdom 5. — Protozoa (First Life). 
The animals placed in this division are extremely simple ; 
they are generally of very minute size, and composed of an 
apparently structureless or but slightly differentiated jelly-like 
albuminoid substance, known as “ sarcode ” ; they have no 
definite pares or segments, no distinct body-cavity, or nervous 
system, nor any definite alimentary apparatus. 
They comprise all the simplest living organisms, such as the 
Infusorial Animalcules, the Amoeba, Foraminifera, Radiolaria, &c. 
The two last-named types have hard skeletons, and are con- 
sequently found as fossils. 
Class 22. — Radiolaria. 
The Radiolaria possess a siliceous skeleton, the parts of 
which are arranged in a more or less radiate manner. The soft 
sarcode, of which the animal’s body is composed, forms a 
central mass, surrounded by a membranous capsule and an 
outer layer containing cell-like bodies, from which extend long 
filamentous ray-like threads of sarcode known as “pseudo- 
podia.” 
The order includes Polycystina , Acanthometrina , Thalassicol- 
lida, and Actinophryina. 
The Polycystina have been found on nearly every ocean door 
both in high and low latitudes. 
Their siliceous skeletons (of extreme microscopic minute- 
ness) have accumulated until they have formed deposits of 
considerable thickness during the later geological epochs, and 
myriads of these exquisite microscopic forms may be obtained 
from many strata in Sicily ; Greece ; Oran, in Africa ; Bermuda ; 
Richmond, Virginia ; and Barba, does. Beds of rock composed 
of these organisms are now known even as far back in time as 
the Ordovician series. 
