GERM CELLS IN PEDICELLINA AMERICANA 25 



The longitudinal split is in these most often completely ob- 

 scured, but I have been able, in a considerable number of 

 cases, to discern it at several points along the course of the 

 fusion (Fig. 84). These rods rarely remain extended, but 

 band into a variety of figures such as S's and shallow U's. In 

 the meantime, the chromosomes as a whole have much concen- 

 trated and are now not much longer than when they appear in 

 the early prophase of the first maturation mitosis. 



Fig. 85 shows such a prophase. The single centrosome and 

 aster have already made their appearance The chromosomes 

 are all very much concentrated and are in just the form in which 

 many appear in the metaphase of the following division. We 

 observe here all the main types pointed out in the discussion of 

 the earlier prophases. There are thus the rings of various 

 forms and the much contracted bars. These are in most cases 

 of dumb-bell shape, showing a constriction in the middle and in 

 some cases a distinct longitudinal split. The chromosome to 

 the extreme left is of particular significance, in that it points out 

 that the rods are also formed by the secondary elongation of 

 the rings along one axis. In this particular instance, the upper 

 portion of the chromosome is already of bar form, while the 

 lower has as yet the form of a ring with the space showing very 

 distinctly. This accessory formation of thick rods from rings 

 is, I believe, of constant occurrence at this period. 



Figs. 86-87 ^^^ early prophases and represent the two main 

 types of chromosome form in the first maturation. Thus, lying 

 side by side, irregularly distributed over the whole spindle, are 

 on the one hand the rings, more or less contracted, and on the 

 other, the bars, somewhat shorter and thicker than before, most 

 of them bent at the middle to form the figure^ . This bending 

 in Pedicellina is comparable with the similar changes observed 

 by Paulmier, '99, in Anasa, Griffin, '99, in TJialasscnia, and more 

 recently by Sutton, '02, in BracJiystola. In these objects, this 

 secondary bending is often complete, thus forming a ring which 

 is split along its whole course. I have not, however, observed 

 any such process in Pedicellina^ where the bending is never much 

 more advanced than to form a semi-circle. 



