Polyploids and Polyploidy¹

Abstract

ANOTHER means of variation, closed to the ordinary diploid, is open to the polyploid. This is variation by loss. Gametes of a diploid which are not equipped with the full chromosome complement are not as a rule functional, but in a tetraploid, where every part of the hereditary material is represented twice in the gametes, loss of a chromosome or part of a chromosome does not necessarily lead to non-viability and is a possible source of a new chromosome balance, a new genetic type. This kind of change is probably responsible for a great deal of the variation in that highly variable species Tradescantia virginiana.