TRICHOPHYTONEAE 



455 



serratus. On the other hand, it must be admitted that Nannizzi reports clostero- 

 spores and aleurospores formed by known Gymnoascaceae when grown on hair, 

 feathers, and bones. Unfortunately, he omits cytologic data. 



Working- with single spore cultures, we must investigate with greater 

 completeness the nuclear histoiy of many more species, before we have a clear 

 notion of phylogeny. This is especially trne in degenerating series where 

 often the extremes of degeneration are more common and first studied. Such 

 was the case of the yeasts for many years. The common beer yeast represents 

 the parthenogenetic end member of a long series whose stages have been so 

 clearly described by Guilliennond during the present century. 



Spring (1931) unsuccessfully attempted to mate strains of three common 

 species to see if they would produce ascocarps. Probably heterothallism is 

 not important in this group. Grigorakis (1931) has secured curious aggrega- 

 tions of hyphae with gelification of the walls and coiling of one filament about 

 another as in perithecial formation when Microspomm felineum and Ectotri- 

 chophyton mentagrophytes (Spirallia asteroides) were grown on media contain- 

 ing glycerol. 



Variations and So-Called Mutants. — Brierley (1929) has summarized the 

 literature on variation in bacteria and fungi very thoroughly. Most of the 

 so-called mutations are not an alteration in the fundamental nature of the 

 germ plasm, usually in a single gene, but are only the result of a recombina- 

 tion of characters already present. It is possible that these changes may 

 result from the loss or the rearrangement of factors when a character is deter- 

 mined by multiple factors. During the numerous vegetative mitoses there is 

 the possibility of an unequal division of chromatin which would alter the char- 

 acter of that portion of the mycelium and of the spores subsequently formed 

 in it. More recent literature is well reviewed by Emmons (1932) in connec- 

 tion with his stud}' of similar phenomena in Acliorion gypseum and Ectotricho- 

 phyton mentagrophytes (T. gypseum). Unfortunately, he has not accompanied 

 his descriptions of cultural characters by cytologic information. Most of his 

 variants arose from a flask culture on horn. Since his variants arose from 

 single spore cultures, they are free from the criticism of those of Biltris (1929) 

 who worked with mass cultures. In most of Emmons' variants, sectors reverting 

 to the parent type were produced. On the other hand, the variant remained 

 constant for twelve transfers (interval not stated) and showed no trace of 

 pleomorphism in 8 months. He could find no evidence of myxochimaeras, nor 

 of cross-fertilization. 



In Emmons' report on his Strain III of his T. gypseum it seems probable 

 that he was dealing with Ectotnchophyton farinulentum rather than E. ment- 

 agrophytes. In this species and E. lacticolor, ultraviolet radiation may have 

 been a factor, since variants developed only after exposure to it. It may not be 

 the sole factor, however, since many other cultures similarly exposed, developed 

 normally. In E. farinulentum, color variants, both red and yellow, arose while 

 in E. lacticolor, the ultraviolet radiation seemed to stimulate the production of 

 nodular organs while depressing the development of aleurospores and spirals. 



