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The life cycle of Achlya involves germination of spores to form coenocytic somatic hyphae, followed by differentiation of hyphal tips into sporangia. From germination to release of new spores occupies 27–30 h. Total lipid made up 10% of dry weight in ungerminated spores. After germination, total lipid fell to 6% of dry weight in 15 h, then rose to7.7% at the time of sporangium formation. Half of the initial loss of lipid took place within 2 h of germination. The ability of Achlya to incorporate [1-14C]acetate into lipid was maximal at the time of sporangium formation, and glycerides were the principal component of total lipid to become 14C-labelled at all stages of the life cycle. Fatty acid synthetase activity measured in cell-free extracts was low in spores and in actively elongating mycelium, but increased during differentiation to a level 15-fold greater than that in spores. Fatty acid oxidation, as estimated by the release of 14CO2 from 1-14C-labelled fatty acids, was also maximal at the time of sporangium formation.

There are four chromosomes present in the somatic nuclei of Trichophyton mentagrophytes. Initially, these chromosomes are ring-shaped but as division proceeds they unfurl becoming rod-like. The spindle apparatus appears to be strand-like and beaded. At mid-division the chromosomes lie in two rows parallel to each other and on either side of the spindle. Each row contains four chromosomes which appear to be attached to the spindle at regions along its length. At the end of division each sister nucleus contains a complement of four chromosomes. Movement of sister nuclei at the end of division appears to be unipolar. The single nucleolus in T. mentagrophytes does not disappear from view during division or immediately after separation of sister nuclei. As a result this nucleolus has been designated as an "undivided persistent nucleolus."