RELATING TO SECONDARY SEXUAL CHARACTERS. 93 



male, while the spayed females also behaved as normal individuals of 

 that sex behave. Kellogg, in 1904, repeated the same operation in the 

 silkworm moth on a small scale with the same results. Kopec and 

 Meisenheimer, in 1909, repeated in a more detailed way Oudemans's 

 work. A further important addition was made by Kopec and by 

 Meisenheimer. They transplanted ovaries into a castrated male and 

 testes into a spayed female. Neither gonad produced any effect on 

 the characters of the other sex. It is interesting to note that the testes 

 underwent their normal development in the body of a spayed female, 

 and even in one with the ovaries present, and that the ovary also under- 

 went normal development in the body of the male. In other words, 

 there is no intolerance of the tissue of one sex to the gonad of the other. 

 This result is all the more unexpected, because other observations have 

 shown that the color of the blood, and its chemical properties, is quite 

 different in the male and female moths of certain species. 



In the case of moths, therefore, if these cases be regarded as typical, 

 the situation from the point of view of sexual selection is much simpler 

 than in birds in the sense that the secondary sexual characters are 

 directly the product of the genetic constituents of all the cells, and not 

 influenced indirectly by the secretions from the testes or the ovaries. 

 Sexual selection, therefore, if it is an agent in the evolution of the dif- 

 ferences between males and females, has acted on the genetic complex 

 to produce these effects on either sex without the result being involved 

 in the condition of the ovary or the testes. 



Regen castrated crickets, Gryllus campestris, in the larval stages and 

 found no effects on the adult structures. The castrated males chirped 

 like normal males and mated with the females. Spayed females were 

 like normal females; they bored holes in the ground, but laid no eggs 

 in them, of course, as the ovary had been completely removed. 



The only genetic evidence in the group of insects, outside of the 

 vinegar fly, relating to the secondary sexual inheritance of the second- 

 ary sexual characters is the following important experiments made by 

 Foot and Strobell : 



The male of one of the bugs, Euchistus variolarius, has a black spot 

 on the end of the abdomen a spot that is not present in the female. 

 Foot and Strobell crossed a female of this species to another bug, 

 E. servus, that lacks the spot in both sexes. The daughters had no 

 spot, the sons a faint spot less developed than in variolarius. These 

 inbred gave (in F 2 ) 249 females without a spot, 107 males with a spot, 

 and 84 males without a spot. The results are explicable on the view 

 that a single dominant Mendelian factor, not-sex-linked, causes the 

 spot in the males, but the presence of the gene in the female produces 

 no effect. The effect, therefore, is sex-limited, i. e., its expression is 

 determined by the rest of the complex male or female. 



The very important breeding experiments carried out by Gold- 

 schmidt on varieties of the gipsy moth should be referred to in this 



