M'CLUNG: CHROMOSOMES OF ANASA TRISTIS. 377 



cessory in the second spermatocyte by its position, as might 

 frequently be done in the first spermatocyte. I am of the 

 opinion accordingly that any identification based upon position 

 alone is not warranted in the case of the accessory chromosome 

 in the second spermatocyte. By this I do not mean that there 

 may not be similar arrangements of the chromosomes in both 

 spermatocyte metaphases, but rather that the opportunities for 

 movements of the chromosomes during the first spermatocyte 

 anaphase and telophase are so great that no rule may be laid 

 down to mark a type of second spermatocyte. (Plate LXXI, 

 figures 11, 12.) 



7. What is the behavior of the accessory chromosome in the 

 second spermatocyte mitosis? 



At this point in the history of the accessory chromosome of 

 Anasa there occurs the wide diversity of opinion between Foot 

 and Strobell and the other investigators who have studied it. 

 The issue is clearly drawn. Foot and Strobell claim that the 

 accessory chromosome is divided in the second spermatocyte 

 as in the first spermatocyte, but Wilson and others are just 

 as positive that it passes undivided into but one of the pair 

 of spermatids formed by the division of each second sperma- 

 tocyte. Issues are joined here on a question of fact, and it be- 

 comes necessary to determine, therefore, whether the accessory 

 chromosome divides in the second spermatocyte metaphase or 

 whether it passes undivided into one of the two daughter cells. 



I must confess that it is a matter of no little astonishment 

 to me that there should be any difference of opinion on this 

 point, because the conditions are so clear and unmistakable as 

 almost to preclude error. A number of photomicrographs of 

 the second spermatocyte anaphase have been prepared from 

 both sections and smears and are reproduced in plate LXXI, fig- 

 ures 13-27. In figure 15 there are shown ten pairs of spermatids 

 as they appeared spread upon the glass slip. This slide was 

 prepared according to the method of Foot and Strobell and 

 shows the cells practically separated so that there can be no 

 question of a later division of the accessory chromosome. In 

 each one of these ten pairs it is clearly seen that one member 

 contains an accessory chromosome while its mate lacks it. The 

 same statement holds true of all similar cells drawn and photo- 

 graphed, and of the thousands of others examined. In no case 



