754 



INHERITANCE 



All members of any one of the four clones belong to the same mating 

 type, and that type is inherited within the clone until endomixis or a 

 new conjugation occurs. In a certain experiment described by Sonneborn 

 (1937), there were fifty-six pairs formed by union of mating types I 

 and II. The four clones from each pair were constituted as shown in the 

 accompanying table. 



In this table the following relations are seen: 



1. In some cases (4 out of 56) all the descendants of the two parents 

 (which were of diverse type) are of the same type. In these cases the 

 type of one of the conjugants and its descendants was changed by con- 



Parents, I X II 



jugation. That is, an individual of type I, receiving a pronucleus from 

 type II, becomes changed to type II, and vice versa. 



2. In some cases the two ex-con jugants of a pair give clones of dif- 

 ferent mating types. 



3. In most cases a single ex-conjugant gives rise to two clones of the 

 same type. 



4. But in some cases a single ex-conjugant gives clones of different 

 mating type. 



Do ex-con jugants that were of a given type before conjugation tend 

 after conjugation to produce descendant clones of that type, or do they 

 produce both types with the same frequency.'^ Sonneborn tested this by 

 mating two clones that were different in appearance, one of each type, 

 then determining the mating type of the descendants. The results were 

 as follows: 



Of 22 ex-conjugants originally of type I, 5 gave descendants of type 

 I only, 7 of type II only, and 10 half of type I, half of type II. Of 25 ex- 



