title: Morphological variations and ectopic pairing of a polytene chromosome of Stylonychia mytilus.
abstract: This paper deals with the description of one polytene chromosome, studied in two strains of Stylonychia mytilus. Phase contrast micrographs of "in vivo" preparations have been utilized. The giant chromosome described here has a large puff in subterminal position that makes it easily identifiable between the other chromosomes of the anläge from the first phases of macronuclear development. Variations of this chromosome during its development and its morphological differences when it comes from strain I or II are described. The idea that the diffuse puffs become the heterochromatic blocks, is newly discussed. This chromosome has been observed isolated, but in some occasions it appears ectopically paired with another chromosome.
authors.affiliation: Centro de Investigaciones Biológicas, Madrid, Spain.
authors.forename: M A
authors.initials: MA
authors.lastname: Jareño