All ciliate possess multiple dimorphic nuclei which have separated the functions of protein synthesis, preformed by the macronuclei

Macronucleus

A macronucleus is the larger type of nucleus in ciliates. Macronuclei are polyploid and undergo direct division without mitosis. It controls the non-reproductive cell functions, the everyday tasks, such as metabolism...

 or somatic

Somatic

The term somatic means 'of the body',, relating to the body. In medicine, somatic illness is bodily, not mental, illness. The term is often used in biology to refer to the cells of the body in contrast to the germ line cells which usually give rise to the gametes...

-nuclei, and heritable DNA replication, performed by the micronuclei

Micronucleus

A the micronucleus is the smaller nucleus in ciliate protozoans, such as the paramecium. In fission it divides by mitosis, and in conjugation furnishes the pairing of gamete nuclei, by whose reciprocal fusion a zygote nucleus is formed, which gives rise to the macronuclei and micronuclei of the...

 or germ-line nuclei. The class

Class (biology)

In biological classification, class is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, order, family, genus, and species, with class fitting between phylum and order...

 Karyorelictea are characterised by an inability to replicate the macronucleus, a process called amitosis

Amitosis

Amitosis is the process by which a cell directly separates, not to be confused with mitosis. Amitosis divides relatively simply, as the nucleus and cytoplasm are directly cut in two. Unlike regular mitosis, no spindles or the formation and appearance of chromosomes are involved in amitosis...

, which must be re-synthesized from the micronucleus every cell division. The majority are unculturable, although clonal lines of Loxodes have been developed. The class is divided into three orders

Order (biology)

In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...

, Protostomatida, Loxodida and Protoheterotrichida, which were defined morphologically

Morphology (biology)

In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....

, but have been confirmed with molecular phylogenetics.