RESULTS OF CROSSING TWO HEMIPTEROUS SPECIES. 



generation. As a matter of fact, however, the spot of Euschistus 

 variolarius is transmitted through the female appearing in a slight 

 degree in the males of the F\. generation and much more intensely in 

 the F 2 generation some of the offspring of this generation having 

 the genital spot quite as conspicuous as that of their maternal male 

 ancestors E. variolarius. Such facts would seem to dispose be- 

 yond question of Castle's suggestion that the factors which produce 

 exclusively male characters must be located in the Y chromosome. 



Sp. Tid. 

 Chromosomes. 



Second Sp. Cyte 

 Chromosomes. ^,A C E X - V 



C E x v 



First Sp. Cyte 



Chromosomes. ~"~A C E 



A B C D E F X 



^B D F X - - 9 



D F x Y< 



^B D F Y - - cf 



Scheme of the two maturation divisions of Euschistus variolarius and Euschistus 

 servus based on the assumption that the first maturation division separates auto- 

 somes of maternal and paternal origin and the second division halves them. The 

 XY chromosomes on the contrary being halved in the first division and separated 

 in the second division. The relative positions of the autosomes may be changed 

 unless definite chromosomes are always destined to the same pole, but reversing 

 their position in this regard does not alter the end result that the only chromosome 

 common to both so-called male-producing spermatids is the Y chromosome. 1 



We may next examine the facts on the basis of the assumption 

 that the factors which produce the male genital spot can be 

 located in the X chromosomes. If this is true then the spot 

 cannot be transmitted through the so-called male-producing 

 spermatozoon for this spermatozoon contains no X chromosome. 



We hoped to be able to test this by fertilizing a pure female 

 E. servus by a pure E. variolarius, but owing to great scarcity of 

 material in the locality where we were working we were unable 

 to find any male variolarius at the time it was possible to attempt 

 this experiment. We were, however, able to cross a pure 

 E. variolarius male with an FI female and compare the male 

 offspring with those obtained by the FI matings. 



1 We have used the method of designating univalents by the letters of the 

 alphabet, bivalents being represented by A B, C D, E F. Only six of the twelve 

 autosomes are designated. 



