172 SEX IN MICROORGANISMS 



including formation of secondary nuclei from chromidia, and the 

 development of amoeboid or flagellated "gametes," and the like. Some 

 of the more recent accounts are those of Hausmann (1920), Hulpieu 

 and Hopkins (1927), and Jones (1928). But Johnson (1930), who 

 reviewed previous work and repeated some of the earlier experiments, 

 concluded that Amoeba proteus reproduces exclusively by binary 

 fission, and that internal parasites, introduction of small amoebae 

 which pass through ordinary filter paper, and mycetozoa derivable 

 from airborne spores could readily explain the great variety of life 

 cycles reported. 



The formation of amoeboid or flagellated "swarmers" has been 

 described for the large multinucleated amoeba, Pelomyxa palnstris, 

 by Greef (1874), Korotneff (1879), Veley (1905), and Bott (1907), 

 (Bott reported fusions of gametes), but Schirch (1914) declared that 

 this amoeba reproduces only by binary fission accompanied by divi- 

 sion of all the nuclei, or by a process of budding, and that previous 

 accounts of sexual reproduction involved parasites. Wilber (1947) 

 stated that "'Pelojriyxa''^ carolinensis {Chaos chaos) and similar multi- 

 nucleated amoebae reproduce only by plasmotomy. Parasites may 

 have been involved in the account of the formation and fusion of 

 flagellated "gametes" from a large multinucleated marine amoeba 

 reported by Schepatieff (1910). 



Older accounts of sexuality in endozoic amoebae, such as that 

 for Entavweba colt by Schaudinn (1903), which was "confirmed" 

 by numerous other authors, are no longer credited. Sexuality in Eii- 

 damoeba blattae has been described or assumed by several authors 

 (for example, Mercier, 1909, 1910; Elmassian, 1909; and Morris, 

 1936) but has not been confirmed. Lucas (1927) separated the amoe- 

 bae of diff^erent sizes in the roaches (previously fitted into one life 

 cycle) into three different kinds: the largest was Endainoeba blattae 

 (Biitschli, 1878); a smaller one was named Entavweba thomsoni; and 

 a still smaller one was called Endolimax blattae. Meglitsch (1940) 

 made an extensive study of the nucleus and of nuclear division in 

 Endamoeba blattae but found no evidence of sexuality. 



Thus we have no convincing evidence of sexuality in amoebae 

 except that for Sappinea diploidea, and even that is incomplete. 



