OBSERVATIONS ON INHERITANCE OF SEX-RATIOS 

 IN MERCURIALIS ANNUA 



Cecil Yampolsky 



Cohimhia University 



The discovery of the sex-chromosomes (so-called) in animals 

 has led to a wide acceptance of the doctrine that sex is inherited 

 in the ordinary Mendelian fashion. Using the Mendelian ter- 

 minology, one or the other of the two sexes is heterozygous for 

 the sex factor. Assuming that the male is heterozygous for the 

 sex factor, a female results from the union of any egg with a 

 female sperm; a male results from the union of any egg with a 

 male sperm. If the female is heterozygous for the sex factor a 

 female results from the union of a female egg with any sperm; 

 a male results from the union of a male egg with any sperm. 

 The question as to when sex is determined receives its answer 

 under the above hypothesis. Haecker's classification of the time 

 when sex may be determined — progamy, syngamy, or epigamy — 

 resolves itself into one group, namely, syngamy. 



So far, cytological evidence for the existence of a hetero- or 

 sex-chromosome in dioecious plants is lacking and the assumption 

 that one or the other of the sexes in dioecious plants produces two 

 kinds of germ cells is based only on indirect evidence in experi- 

 mental breeding. Correns and Bateson working almost simul- 

 taneously on Bryonia dioica and Bryonia alba, two species of the 

 genus Bryonia, the former of which is dioecious, the latter monoe- 

 cious and both of which cross readily, arrived at opposite con- 

 clusions. Correns concludes that it is the male of Bryonia dioica 

 that has two kinds of pollen, male and female, while Bateson 

 concludes that the female of Bryonia dioica bears two kinds of 

 eggs, male and female. The following are the results of the 

 crossings of Bryonia dioica with Bryonia alba which Correns and 

 Bateson secured: 



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