Fig. 63. Conjugation of chromosomes (side to side union) in the spermatogenesis of Batracoseps. (After Janssens.)
When the chromosomes separate at the next division of the germ cell the part on one side passes to one pole, the part on the other to the opposite pole, (figs. 64 and 65). Whenever the chromosomes do not untwist at this time there must result an interchange of pieces where they were crossed over each other.
Fig. 64. Scheme to illustrate a method of crossing over of the chromosomes.
Janssens has found at the time of separation
evidence in favor of the view that some such interchange probably takes place.
We find this same process of interchange of characters taking place in each of the other three groups of Drosophila. An example will show this for the Group II.
