2 MORPHOLOGIC VARIATION 



fore that we stop to evaluate the data and critically analyze the 

 logic of these disciples of the "newer biology" of bacteria. 



While occasional contributions have been made by a number 

 of other authors, the principal members of this modern school of 

 pleomorphists are Almquist, Hort, Lohnis, Mellon, and Enderlein. 

 It is noteworthy that, excepting Almquist, all of these men made 

 their initial contributions to the subject in the years 1915-1917. 

 For details of their work the reader must consult their published 

 papers, the most important of which are listed at the end of this 

 work. But we may with profit summarize briefly here the ideas 

 of each concerning the nature of the morphologic variations of 

 bacteria. 



Almquist has made observations of various members of the 

 colon-typhoid-dysentery group of organisms, especially in old 

 cultures kept at low temperatures on drying media. In his earlier 

 work he has particularly emphasized the formation of exogenous 

 globular forms which are produced from the normal rod forms by 

 lateral or terminal budding. If these give rise again to rod forms 

 directly they are called conidia; if they form new globular forms 

 endogenously they are sporangia, and the cells so formed are 

 gonidia; this process, however, may result from a sexual conjuga- 

 tion in which case the mother cell is an oospore, the male element 

 being a very small conidium called an antheridiospore. From 

 cultures containing these conidia a new type which bred true was 

 separated by filtration through Berkefeld filters, the obvious con- 

 clusion being that the cells which passed through were minute 

 conidia (1911). These new types when used as antigens gave 

 rise to agglutinins for the parent culture. In later papers (1924) 

 he claims to have proved the occurrence of sexual reproduction 

 by the production of hybrid crosses between typhoid and dysen- 

 tery organisms, some of the colonies from mixed cultures of these 

 two organisms being agglutinated by both serums; and by the dis- 

 covery of haploid and diploid phases in the nuclei, the diplonts be- 

 ing large globular forms with a nucleus twice as large as in the 

 normal, haplont rod forms. 



Hort, believing that all of the phenomena observed in epi- 

 demic cerebrospinal meningitis could not be explained by the cur- 



