i 9 u] SHU LL REVERSIBLE SEX-MUTANTS 335 



Particular attention should be given to only two points in this 

 table until after the results secured in the second generation have 

 been considered. The assumptions which form the basis of the 

 first section of the table lead to the expectation (a) that females 

 derived from hermaphrodite families, whether they be fertilized 

 by normal males or by their hermaphrodite sibs, will yield families 

 in which the male offspring are hermaphrodite and normal male in 

 equal numbers; and (b) 'that the hermaphrodites of the second 

 generation when used to fertilize females from normal male families 

 will produce no hermaphrodites, but only females and males. The 

 alternative assumptions involved in the second and third sections 

 of the table, on the other hand, lead to the expectation that, re- 

 gardless of the origin of the female, no hermaphrodites will be pro- 

 duced normally, except when fertilization is brought about by 

 sperms from a genetic hermaphrodite, and then the result will always 

 be the same whether this hermaphrodite was a mutant or whether it 

 was derived from an antecedent hermaphrodite. 



We may now proceed to examine the results of the crosses. 

 This will be most easily accomplished by considering each type 

 of cross separately in the following fourteen cases. In the model 

 pedigrees, illustrated under each case, the oldest ancestors entered 

 in the diagrams are females and males both of which came from 

 normal families, whose matings had been controlled during at 

 least three still earlier generations, and which are known to have 

 been in each such previous generation the result of crosses between 

 females and normal males, and to have belonged to families in 

 which no hermaphrodite mutants appeared. In the diagrams 

 all male and hermaphrodite individuals which appeared as mutants 

 are indicated as such, and it should be understood that any male 

 or hermaphrodite not so marked was a member of a family which 

 consisted of a normal proportion of its own type, that is, either 

 male or hermaphrodite. 



CASE I 

 CROSSES OF GENETIC HERMAPHRODITE MUTANTS WITH FEMALES 



Only 2 of the 8 plants recorded as hermaphrodites in 1909, in 

 otherwise normal male families, were successfully used for breeding. 

 One of these, bred to 2 different unrelated females, produced 72 



