SEGREGATION OF HOMOLOGOUS CHROMOSOMES 



463 



one. For example, individual number 3 has five Stenobothrus 

 rings and three J-shaped tetrads making thirteen V-shaped dyads 

 derived from the tetrads in question — that is, not including num- 

 bers 4, 2 or 1. We have then in these nine (fig. 1) tetrads, which 



Text-fig. 1 Curves showing the number of atelomitic dyads, exclusive of 

 chromosomes number 1, 2 and 4. The abscissae represent the number of such 

 dyads, the ordinates the number of individuals, the broken curve includes data 

 from twenty additional animals of form 'B.' 



are concerned in the changes, the possibility of eighteen atelo- 

 mitic dyads. The two solid curves each represent the same 

 number of individuals, thirty-one, the total number in the col- 

 lection of form 'A'. There were twenty more animals of form 

 'B' which have been studied but not included in the plates, since 



