The nuclear conditions in the life history of Cutleria multifida may be summarized as follows: 1. The nucleus of both male and female plants contains 24 chromosomes, and the male and female gametes contain the same number. 2. In the union of gametes the number is doubled, and 48 chromosomes appear in the sporelings, which develop into the Aglaozonia form of Cutleria. Therefore, the individual bearing the name of Cutleria multifida represents the gametophytic phase of the species, 24 being the gametophytic number of chromosomes; and the Aglaozonia form of Cutleria represents the sporophytic phase, 48 being the sporophytic number. 3. Aglaozonia reptans contains 48 chromosomes, and the number is reduced in zoospore formation, the zoospore containing 24 chromosomes The zoospore with the reduced number of chromosomes germinates without conjugation. The individual grown from the germinating zoospore presents a striking similarity to the young form of Cutleria in nature and contains 24 chromosomes, the same number as the latter. Therefore it is evident that the individual bearing the name of Aglaozonia reptans represents the sporophytic phase of the species, 48 being the sporophytic number of chromosomes, and that the gametophytic phase is represented by the individual grown from the zoospore and resembling the young form of Cutleria in nature. It is certain that Aglaozonia reptans as it occurs in nature is identical with the Aglaozonia form of Cutleria multifida as developed in cultures and now determined to be the sporophytic phase of the species. 4. Therefore, Cutleria multifida and Aglaozonia reptans represent respectively gametophytic and sporophytic generations of a single species, the two generations alternating in the life history of Cutleria. 5. The female gamete of Cutleria may germinate apogamously. There is no irregularity in the mitotic process, 24 chromosomes being invariably present. The individual produced, in its early development differs somewhat from the product of the fertilized gamete, but the fate of the apogamous individual was not determined.