- a colonial radiolarian, the bright spots being the central capsules of the organisms which make up the colony. Up to 5000 capsules may be present in a colony. These colonies are like long sausages up to several centimetres in length. There is a sheath of organic material, and this may be referred to as gelatin. The colony has a segmented appearance because the components of the colony lie in a matrix around large vacuoles or alveoli. This is an example of one of the four types of large amoebae which is common in the marine water column. Image by Dave Caron.