LINKAGE 



385 



there are those who deny any fusion a1 all between the members of the 

 pair, holding rather that their identity is do1 impaired in any way during 



Fig. 149. — The behavior of the conjugating homologous chromosomes according t-> 

 the Chiasmatype Theory of Janssens. Single crossing over at left; double crossing over 



at right. (Adapted from Babcock and Clausen.) 



CHIA3I1ATYPC • JAN33EM5 I90». 







v> 







00 



Fig. 150. — Crossing over between 2 of the 4 chromatids of the chromosome tetrad, giving 

 2 crossover and 2 non-crossover gametes. (Adapted from Janssens, 1909 



Fig. 151. — Chromosomes of Balracose.ps attenuatns, Bhowing chiasmas. (After Janssens.) 



their intimate association: the two chromosomes appearing on the first 

 maturation spindle are exactly the same as those which conjugated. 



