GERM CELLS IN PEDICELLINA AMERICANA 45 



attitude of the majority of the workers on these forms. On the 

 other hand, in those cases, where the early history of the chro- 

 mosomes is more fully known, and where from the final consti- 

 tution of these structures a reduction division almost certainly 

 occurs, there opinion is much divided as to whether the first or 

 the second division is the reducing one. The chromosomes, 

 mainly in the form of tetrads, rings and crosses, are often so 

 symmetrical that the two axes, i. e., the longitudinal and the 

 transverse, cannot be distinguished. In Pedicellina^ while these 

 types of chromosomes occur, they are not the prevailing types. 

 Fortunately, the peculiarly favorable bars which persist from 

 the earlier growth period and whose history is very completely 

 known, occur in the large marjority of instances and are so 

 located in the spindle throughout the phases of division, as to 

 leave no doubt that the first maturation division is, in both ^g^ 

 and sperm, the reducing one. In this regard, the condition in 

 Pediceliina are in accordance with the results of a constantly 

 increasing number of workers, botanists as well as zoologists, 

 whose results are based on a particularly full history of the 

 earlier stages of the chromosome formation. 



At this point the Platodes present very instructive conditions 

 for comparison. At the end of the growth period both the 

 rings and ellipses so characteristic of Pedicellma, and the bar- 

 shaped figures are present. While on this point all the workers 

 are, on the whole, agreed, a difficulty in the interpretation has 

 of late been introduced in the last work of Schockaert, '02, on 

 the ovogenesis of Thysanozoon. This author, in a most pains- 

 taking work, confirming the presence of the figures of the 

 various forms noted above, and agreed further with this work 

 on Pediceliina in considering the first maturation division the 

 reducing one, comes to this similar conclusion on grounds 

 which are entirely at variance with the process described, not 

 only in this work, but in nearly all of the other studies on the 

 Platodes. This is all the more striking in the light of what I 

 take to be a complete correspondence in the earlier changes in 

 the germinal vesicle in the two forms. After a synapsis stage 

 coincident with the telophase of the last oogonial division, the 



