104 SEX IN MICROORGANISMS 



isogamy, would hardly be complete without some reference to the 

 heated controversy which raged between biologists at Berlin and 

 Prague during the 1920's and 1930's. Hartmann (for example, 1932, 

 1943) adopted the theoretical anthropomorphic concept, borrowed 

 perhaps from Aristotle (for example, 1910), that there can be no 

 sexual union without sexual differentiation. If compatible gametes are 

 morphologically and, as in homothallic species, genetically identical, 

 then, he postulated, there must nevertheless exist some invisible phys- 

 iological difference between them, and the strain is said to possess 

 "bisexual potency." On the other hand, Mainx (1933) and Czurda 

 (1933a) saw no reason for adopting this hypothesis, for which they 

 found no corroboration in their experimental observations on algae 

 and other organisms, and they freely accepted the fusion of identical 

 cells in syngamy, just as it occurs in the hyphal anastomoses of fungi, 

 or the formation of plasmodia in Myxomycetes. 



And then, in the early 1930's, Franz Moewus, a student of Kniep 

 and Hartmann at the Kaiser Wilhelm Institute, reported experimental 

 support for the theory of bisexual potency from his investigations 

 of unicellular algae such as Frotosiphoii (1933, 1935a), Folytoma 

 (1937), and Chlamy domonas eugmnetos synoica (1938a). In a clonal 

 culture of such homothallic, isogamous forms, both "male" and "fe- 

 male" gametes are said to be produced; and, when pairing takes place, 

 unless precisely similar numbers of the two mating types are present, 

 there will of necessity remain a few residual gametes {Restgameten) 

 of the supernumerary sex. Suspensions of residual gametes from sev- 

 eral cultures, freed in some way from already paired cells, may be 

 tested for mating type by mixing them in combinations of two or 

 with heterothallic tester stocks and observing in which mixtures mat- 

 ing is reinitiated. Lerche (1937) reported preliminary observations on 

 Haematococcus, in which, using morphologically distinguishable red 

 and green clones, she was able to demonstrate the regularity of resid- 

 ual gamete fusions; and Moewus (1940a) carried out a similar experi- 

 ment, using the marker "eyeless," in Botrydiinn granulatwn. But 

 Pringsheim and Ondratschek (1939) in Prague sought in vain to con- 

 firm Moewus' assertions about residual gamete behavior in Folytoma 

 and Protosiphon, thereby lending further weight to the initial objec- 

 tions of Czurda (1933a). Pringsheim and Ondratschek pointed out 

 that residual gametes could hardly be expected to behave in the man- 

 ner described by Moewus in organisms where sexuality is claimed to 



