Visual form discrimination on the basis of relative distribution of light.

Whittaker's five-kingdom classification (1) of living organisms is possibly the most satisfactory yet proposed. It should provide not only a more sensible system of classification but also a more logical means of presenting this subject to students. With the object of strengthening rather than criticizing the proposal, I recommend an alteration in treatment of a group with which I am familiar. The change would be in line with Whittaker's emphasis on mode of nutrition. It is unlikely that any members of the subkingdom Gymnomycota, which (excepting labyrinthulids) ingest their food, are related to what are commonly considered the true fungi, which have absorptive nutrition. Therefore, I suggest that this group be transferred to the kingdom Protista, possibly as a subkingdom, with the bulk of the protists in a separate subkingdom. It might then be expedient, at least tentatively, to include the plasmodiophorids and protomyxids (plasmodial forms living in the cells of other organisms) in the Gymnomycota. The latter are known to ingest, and there is evidence that the former may ingest as well as absorb their nutrients. Whittaker's statement that his three phyla of Gymnomycota have probably had three separate phylogenetic origins is not supported by our recent findings (2) on a still simpler and more primitive group, the protostelids, which are clearly allied with the Gymnomycota. Evidence has been presented in support of the origin of a major portion of the cellular slime molds from the protostelids, and there is also a fair possibility that plasmodial slime molds may have had their origin in this group. In addition, there are reasons for believing that the cellular slime molds are not a monophyletic group (3). Finally, there are probably more forceful arguments for allying the hyphochytrids, which have absorptive nutrition, with the aquatic fungi rather than the protists. Though their origin may have been independent of other groups of fungi, a good case can be made for their derivation from the laterally biflagellate fungi (Oomycota) through loss of the posterior flagellum. LINDSAY S. OLIVE Department of Botany, University of North Carolina, Chapel Hill 27514