Heredity and sex . Fig. 17. — Male and female Herculesbeetle. (After Kingsley.) tinue until the female is found, and the drama of sexis finished. Mast has recently shown that the female firefly doesmore than simply respond to the signal of the a male flies above and to the right of the female, shebends her abdomen so that its ventral surface is turnedupward and to the right. If the male is above and tothe left, the light is turned in this direction. If the male THE EVOLUTION OF SEX 31 is directly above, the abdomen of the female is twistedalmost upward. But if the male is below her, sh
Heredity and sex . Fig. 17. — Male and female Herculesbeetle. (After Kingsley.) tinue until the female is found, and the drama of sexis finished. Mast has recently shown that the female firefly doesmore than simply respond to the signal of the a male flies above and to the right of the female, shebends her abdomen so that its ventral surface is turnedupward and to the right. If the male is above and tothe left, the light is turned in this direction. If the male THE EVOLUTION OF SEX 31 is directly above, the abdomen of the female is twistedalmost upward. But if the male is below her, she emitsher light without turning the body. In the firefly theevidence that the phosphorescent organ is of use inbringing the sexes together seems well Fig. 18. — Male and female firefly. Whether all secondary sexual organs are useful inmating is a question that must be referred to a laterchapter. THE SEXUAL INSTINCTS Side by side with the evolution of these many kindsof structural difference the sexual instincts have is only in the lowest forms that the meeting of theegg and sperm is leftrto-chance. The instincts thatbring the males and females together at the matingseason, the behavior of the individuals at this time in 32 HEREDITY AND SEX relation to each other, forms one of the most curiouschapters in the evolution of sex, for it involves court-ship between the males and females; the pairing orunion of the sexes and subsequently the building ofthe nest, the care, the protection and feeding of theyoung, by one or both parents. The origin of thesetypes of behavior is part of the process of evolution ofsex; the manner of their transmission in heredity andtheir segregation according to sex is one of the mostdifficult que
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Keywords: ., boo, bookcentury1900, bookdecade1910, booksubjectsex, bookyear1913
