This process is guided by long RNAs derived from the parental macronucleus. Inside, there is a curved, transverse macronucleus and round micronucleus near it. The polyploid macronucleus found in ciliates divides amitotically. Contractile vacuoles are located between or beside the macronucleus and vestibule. The chromosomes of the macronucleus are also unusually short. Ciliates contain two types of nuclei&colon; somatic "macronucleus" and the germline "micronucleus". Usually only the macronucleus and sometimes cilia and contractile vacuoles are visible in the cyst. "Paramecium" have two nuclei (a large macronucleus and a single compact micronucleus). There is apparently little, if any, DNA damage in the new macronucleus. Trophozoites possess both a macronucleus and a micronucleus, and both are usually visible. These experiments indicated that the macronucleus, rather than the cytoplasm, is responsible for clonal aging. Each cell has one (often elongated) macronucleus and several micronuclei. The macronucleus of ciliates for example contains hundreds of acentric chromosomes. They are unusual among eukaryotes in that reproduction involves a micronucleus and a macronucleus. Ciliates have cells that contain two nuclei&colon; a macronucleus and a micronucleus.