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THE AMERICAN NATURALIST [Vol. XLII 



Lygaeus), or have entirely disappeared (as in Protenor), all the 

 eggs may then carry idiochromosomes of like activity and there 

 is no need for selective fertilization. These cases accordingly 

 seem to lend themselves for interpretation very well to the prin- 

 ciples above stated for sex-determination in Bryonia. In Men- 

 delian terminology, females are pure zygotes, i. c, homozygotes; 

 males are hybrids, i. e., heterozygotes. Segregation takes place 

 at maturation and produces by the homozygote organism one 

 kinds of germ cells and by the heterozygote two kinds, i. e., male 

 and female in sex-tendency. 



The physiological male or female property of the germ-cells 

 which provides for their union and what relates thereto, must 

 not be confounded with the male and female tendency of the 

 germ-cells, or the disposition to give rise to descendants whose 

 germ-cells are again male or female. Though these principles 

 of sex-determination and inheritance discovered for higher 

 plants may not be capable of universal application, there are 

 several points in which the different methods may agree: (1) 

 That each germ-cell has originally a fixed sex-tendency; (2) that 

 the germ -cells of one sex (either the male or the female) have 

 only one and the same sex-tendency, and those of the other partly 

 the one, and partly the other; and (3) that a primarily fixed 

 differentiation in the developmental vigor of the germ cells with 

 different sex-tendencies that unite at fertilization, brings about 

 a decision favorable to one or the other sex. 



(No. 503 was issued on November 20, 1908.) 



