GERM CELLS IN PEDICELLINA AMERICANA 21 



chromosomes which have arisen through a longitudinal split, 

 and have remained attached at one end, but rather that these 

 represent the univalent chromosomes which united at the last 

 oogonial telophase. 



As will appear from a closer examination of the figures there 

 are at the apices of the V's, in a great number of cases, the deep 

 staining knobs (Figs. 67, 69, 70) which were described at the 

 same point in the V's of the late synaptic telophase (Fig. 66). 

 Since that period the only new element that has appeared is the 

 nuclear membrane of the reconstructed nucleus. The chro- 

 mosomes have preserved not only their characteristic form, but 

 their position as well. The presence of these synaptic knobs 

 cannot by any possibility be interpreted as chance thickenings 

 along the chromosomes ; the constancy of their location and 

 the frequency of their occurrence point very strongly to the 

 conclusion that they represent the points of union of the uni- 

 valent rods, and as such, they would correspond to the linin 

 fibers connecting the two arms at the apices of the V's, as de- 

 scribed by Montgomery, first for Peripatiis, '99, and later for 

 the Amphibian spermatocyte, '03. 



As the growth period begins, the cytoplasm becomes easily 

 distinguishable in contrast with the previous stage, and the 

 chromosomes, moved away from the one end of the nucleus, 

 now lie apposed on nearly all sides to the nuclear membrane 

 (Figs. 71-72). There is as yet no sign of granulation of the 

 chromosomes. It is usually, also, at about this time (although 

 there is much variation in this regard) that a longitudinal split 

 in the arms of the V's makes its appearance (Figs. 73-74). 

 The splitting often begins at one end of an arm and passes 

 upward toward the point of synapsis, though in many cases the 

 early splitting may occur in both arms at the same time (Fig. 

 75). Fig. 76 shov/s a little later stage where most of the 

 chromosomes are already divided and have begun to show a 

 distinctly granular appearance. This process, too, is extremely 

 variable in the time of its occurrence, and is not necessarily 

 connected with the longitudinal split, which, in most cases, 

 takes place before the granulation has begun. This is impor- 



