228 V. A. DOGIEL 



Ample evidence for this is afforded by the cross-migration of 

 ' male ' pronuclei, and by the reconstruction of the nuclear 

 apparatus and skeleton in microconjugants. Of course, we 

 could suppose that during the progamic fission the material of 

 the micronucleus is distributed unevenly, so that the male 

 elements are taken by the microconjugant, the micronucleus 

 of the macroconjugant getting only the female ones. If so, then 

 before and during the conjugation one specimen acts as a male, 

 another as a female, returning only after conjugation to the 

 hermaphrodite state. But there is no real evidence in favour 

 of this view, and the possibility of conjugation between two 

 macroconjugants (in 20 per cent.) speaks against it. 



But even so, we can still see in the complex processes of 

 conjugation in 0. janus the first hint of approaching sexual 

 differentiation. Indeed, conjugation seems to have become 

 impossible between two microconjugants, and this circum- 

 stance raises them physiologically to quite another category 

 in comparison with the macroconjugants. This loss of the 

 faculty to conjugate inter se speaks clearly in favour of 

 a male tendency in the microconjugants. Then, again, certain 

 abnormal cases of conjugation also confirm my view of the 

 possible future transformation of microconjugants into males. 

 Among about a hundred micro-exconjugants which came under 

 my inspection there happened to be the following abnormal 

 specimens. One exconjugant, instead of old macronucleus + 

 synkaryon (or its derivatives), possessed only the old macro- 

 nucleus. Another one, instead of having two pronuclei or 

 a syncaryon, showed only one small nucleus of micronuclear 

 type and the remains of the old macronucleus. A few abnormal 

 pairs of conjugants permit us to guess how such exconjugants 

 arise. In one of the pairs (PI. 17, fig. 11), for instance, the 

 microconjugant contains only a macronucleus, while the 

 macroconjugant has got the macronucleus and four micro- 

 nuclei (PI. 17, fig. 11, Mij-Mi^). One of the latter (MiJ is 

 lying in the hind half of the body, another one (Mi^) just 

 at the line of junction of the conjugants, on the way to the 

 partner, while the remaining micronuclei {Mi^ and Mi^) lie 



