376 KANSAS UNIVERSITY SCIENCE BULLETIN. 



tention to figures 6, 7, 8, 9, 10, plate LXXL These show that 

 while the time of division is later than that of the other chro- 

 mosomes the actual separation occurs and the halves of the 

 divided accessory chromosome may, in each case, be seen in the 

 daughter cells. No instance could be observed where there 

 could be doubt of this fact. The clearness of these phenomena 

 is due to the fact that the accessory chromosome remains, as in 

 the prophase, distinct from the other chromosomes, so that it 

 can be followed even into the telophase. As will be seen later, 

 the same aloofness on the part of the accessory chromosome 

 is encountered in the second spermatocyte and is so marked 

 that there is no difficulty in tracing its behavior. 



6. What is the behavior of the chromosomes in interkinesis? 



The interval between the two spermatocyte divisions is com- 

 paratively brief and the changes in the relative positions of 

 the chromosomes slight. While the chromosomes mass together, 

 the outlines of the individual elements may be seen clearly in 

 favorable preparations of the telophase. Since the whole 

 daughter chromosome complex travels to the pole at about the 

 same rate, its members at the end of the movement lie at 

 approximately the same level. When therefore the second 

 spermatocyte spindle is formed there is little or no change in the 

 positions of the chromosomes, and the equatorial plate of the 

 metaphase corresponds in general with that of the first sperma- 

 tocyte, from which it was derived. While this is true, the slight 

 movements of all the chromosomes during their poleward mi- 

 gration usually results in a destruction of the typical ring 

 arrangement so characteristic of the first spermatocyte. Be- 

 cause of its isolated position and somewhat greater variation 

 of movement in the anaphases, the accessory shows more 

 marked diff'erences in position in the equatorial plate than the 

 other chromosomes. If it has moved toward the pole at the 

 same rate as the rest of the complex and maintains its position 

 during the telophase it will then be found upon the periphery 

 of the equatorial plate in the second spermatocyte. If, on the 

 contrary, as often happens, the movement is slightly slower 

 than that of the other chromosomes and it swings around un- 

 der the mass during the anaphase movements it will later ap- 

 pear within the group of chromosomes in the resulting equa- 

 torial plate. It is not possible, therefore, to recognize the ac- 



