EES 207 - September 29 Earth and Environmental Sciences Invertebrate Paleontology Fall 1999 September 29. In the old two kingdom model protists fell under the 'animal' kingdom because they did not photosynthesize. This division is further subdivided on the basis of the possession of different varieties of chlorophyll molecule and other pigments that give cells varying colors. They are between 30-1500 ms in diameter.
Radiolarians are planktonic amoebic protistans.
Their protoplasm is divided into endoplasm and ectoplasm . These are separated by a perforated organic layer called the central capsule . Extra-capsular protoplasm contains the symbiont algae during the day. The siliceous skeleton is built around the central capsule, so it is completely surrounded by the protoplasm. Little is known about the biology of radiolarians, but they have been observed to undergo binary fission.