PROTOZOA 



29 



fertilization develop parthenogenetically (p. 78): it is interesting 

 that one of these gametes is a functional male. Individuals of 

 Polytoma which are potential gametes will grow and divide, and the 

 same is true of the gametes of some species of Chlamydomonas when 



Fig. 26. Conjugation of ciliates. A, Paramecium. B, Vorttcella. Both at the 

 moment of the exchange of male pronuclei, meg. fragments of disintegrating 

 meganuclei ; mi. micronuclei : in each the male and female pronuclei produced 

 by the division of a single nucleus still hang together by their spindle, but are 

 parting, the male to pass into the other conjugant, the female to remain behind ; 

 mi.' abortive division products of the original micronucleus. 





Fig. 27. A diagram of the behaviour of the micronuclei during the conjuga- 

 tion of Paramecium caudatum. From Borradaile. The white circles represent 

 the portions which degenerate. 



syngamy has been missed. The endomixis of ciliates (p. 30) is a 

 phenomenon of this kind. 



Since it is comparatively easy to observe the conditions which pre- 

 cede and the results which follow syngamy in the Protozoa, many 



