VARIATION I N STREPTOML’CES

There can be no fundamental progress in our understanding of variation in Streptomyces until we know more about the organism itself. We need, first of all, to know whether or not the substratal and aerial mycelia are constitution-ally different. This will require intensive studies in cytology and morphology, fields which can hardly be claimed to be enjoying a heyday a t the present time in biology. The proponents of a two-phase life cycle who postulate a haploid substrakal mycelium and diploid aerial growth have been principally the European in-vestigators Badian (1936), von Plotho (1940), and Klieneberger-Nobel (1947). Badian (1936) claimed that the chromatin is distributed through the hyphae as chromosomelike bodies which unite just before conidial formation, so that each conidium has a bivalent chromosome. When a conidium germinates, this bivalent chromosome undergoes two divisions, one of them a reductional division. At the same t h e, from one to three germ tubes arise, each of which receives one of the four daughter chromosomes. The remaining chromosom