156 Life and Death, Heredity and Evolution 



AA 



AB 



BB 



Figure 43a. Biparental inheritance and the production of diversity 

 by conjugation, in Chlamydomonas, after Pascher (1916), from Hart- 

 mann. 1 A and B, the two parental species. AA, cyst formed by con- 

 jugation of two individuals such as A. BB, cyst formed by conjugation 

 of B. AB, cyst formed by conjugation of A with B. a, b, c, d, the 

 four types of free living individuals resulting from the conjugation of 

 A and B. 



In this cyst the reducing divisions occur (Lecture VII), 

 and it divides into four free-swimming individuals which 

 when the conjugation was between two similar parents, are 

 like those parents. These free individuals now reproduce by 

 fission in the usual way. 



When the cyst had been formed by conjugation of the two 

 diverse kinds of parents A and B, the progeny show a num- 



1 Hartmann, M., Zeitschr, f. Ind. Abst., September, 1918. 



