284 THE EVOLUTION OF THE METAZOA 



say that they copulate or pair without developing an intimate 

 contact; they each mutually encyst the other. The gynogametes 

 are produced after multiple divisions by one individual which 

 functions as a female, and androgametes by the other in- 

 dividual which functions as a male. They become "free" even 

 if they remain within the wall of the cyst and are in this way 

 separated from the environment. Here the gametes can meet 

 in masses to copulate and to produce zygotes. Yet in this way 

 the whole mass of the cytoplasm of the gamonts is not used 

 up. A considerable part of it remains as a remnant w'hich is 

 destined to die. The zygotes naturally become finally free. It 

 should also be mentioned that in the case of a typical oogamy, 

 one gynogamete only can be developed by way of meiosis by 

 a gamont or by a gametocyte w^hich can be produced by a 

 gamont (in this case the gamont actually becomes a praega- 

 mont), while the number of androgametes can be very large. 

 The hermaphrodite state emerges at the first sight quite 

 unexpectedly among such animals that had originally adopted 

 the system of tw^o different sexes. It appears, it seems, without 

 a true motivation. This phenomenon, however, can be more 

 easily understood if the generally valid and well-founded 

 theory of a potential bisexuality is taken into consideration 

 (Hartmann et al.). Less easily understood are the immediate 

 reasons which can lead in individual cases to an introduction 

 or to an omission of the hermaphrodite state. It is well known 

 that in each individual which is normally gonochoristic 

 (dioecious) the sexual biochemistry of one sex only is pre- 

 valent, while the biochemistry of the opposite sex remains 

 inactive. An initially indifferent gametocyte can become 

 divided by way of heterocyclic (not equivalent) divisions, and 

 under special circumstances it can thus develop into units with 

 two sexually opposed orientations. Such a development must 

 be supposed to have taken place during the transition from the 

 polykaryonic Zooflagellata to the primitive Ciliata. One of the 

 great advantages of the polykaryonic theory, if compared with 

 the colonial theory, an advantage w^hich must not be under- 



