24 MEDICAL MYCOLOGY 



In spite of this removal and retardation, caryogamy always occurs in 

 definite organs. The organs in which the fertilization processes are completed 

 and the dicaryon ends are called zeugites. As caryogamy is delayed until 

 the necessity for meiosis appears, the zeugites also frequently function as 

 gonotoconts. These two processes, the transformation of the cells which com- 

 plete the sexual act and the division of the sexual act itself into plasmogamy 

 and caryogamy, separated in time and space, are both fundamental and very 

 useful in the study of phylogeny and classification. 



In the present state of our knowledge, the various groups of fungi are 

 apparently polyphyletic and unrelated. Some members seem more closely 

 related to other groups of plants than to other groups of fungi; e.g., the 

 Chlamydobacteriales and perhaps the Thiobacteriales seem more closely re- 

 lated to the Myxophyceae than they are to other groups of bacteria or of 

 fungi. 



The following list of classes of fungi illustrates the main subdivisions 

 while not necessarily assuming that all the fungi of these larger groups are 

 monophyletic. In time some of these groups will probably be further divided, 

 e.g., the Phycomycetes seem quite heterogeneous. For our purposes, how- 

 ever, only one order of these, the Mucorales, has been shown to have members 

 attacking man and other mammals, and needs consideration here. 



Schizomycetes : bacteria in the larger sense. 



Myxomycetes: slime molds, having many resemblances to Protozoa in 

 some stages of their life cycle. 



Phycomycetes: coenocytic fungi of varied origin and relationship. 



Ascomycetes : a large poljonorphic group with a common method of spore 

 formation in asci. 



Basidiomycetes : a very large group with spores borne on a specialized 

 gonotocont, the basidium, furnishing most of the conspicuous fungi. 



Fungi Imperfecti : a heterogeneous group whose life cycles are unknown 

 in full, or which have degenerated until sexuality has been lost, provisionally 

 grouped together until they are better known. 



Schizomycetes. — Bacteria. While this group is by far the most important 

 from the standpoint of the physician and the surgeon, it is also the best known 

 to the medical profession and will not be given further consideration here. 

 The bacteria seem almost wholly unrelated to the other groups of fungi, and 

 some of the higher forms are suggestive of Myxophyceae which have lost 

 their chlorophyll. 



Myxomycetes. — The slime molds are a very interesting group with many 

 stages suggestive of similar conditions found in the Protozoa, especially the 

 Rhizopoda, while other stages are analogous to those in other groups of fungi. 

 The stages commonly observed being plantlike, they have been studied mostly 

 by botanists and only in the last decade has any long continued or thorough 

 attempt been made to follow the life cycle in detail or to study the cytology. 

 At present the group is known to cause plant diseases but has not been 

 suggested in relation to animal disease. Any related organisms attacking man 

 have undoubtedly been studied and classified as Protozoa. 



