iqi2] SHARP— SPERMATOGENESIS IN EQUISETUM 99 



In other cells of the same antheridium only this pair is present, 

 the other bodies, if formerly present, having been resorbed. 



One can hardly speak conclusively regarding all points in the 

 history of such minute structures. The evidence at hand, however, 

 inclines the present writer toward the belief that the original single 

 granule, which by division gives rise to the two blepharoplasts, is 

 in some cases one of a number which may appear de novo in the 

 cytoplasm and start development. 



The two blepharoplasts, which lie very close together for a little 

 time immediately following their formation from a single body, soon 

 begin to move apart. As they do so a very distinct central spindle 

 develops between them, so that a faint but undoubted amphiaster 

 is formed (figs. 6, 7). In some preparations the rays on the side 

 toward the nucleus are somewhat heavier than the others and form 

 a distinct cone (fig. 6). This feature is not made out in all cases. 

 A line joining the two blepharoplasts may lie in any position with 

 respect to the nuclear membrane, though the situation shown in 

 fig- 6 is the most usual one. The blepharoplasts continue to 

 separate, moving in paths close to the nuclear membrane, until 

 they lie 180 apart (figs. 8-12). During the earlier stages of the 

 migration the central spindle gradually fades out (fig. 8). The 

 astral radiations persist, and when the blepharoplasts reach polar 

 positions those on the side toward the nucleus become more distinct, 

 being especially conspicuous when the blepharoplasts move a little 

 distance away from the nucleus (fig. 13). They form two cones 

 with the blepharoplasts at their apices, while the radiations extend- 

 ing in other directions remain very faint. The rays of the cone 

 do not diverge from a single point on the blepharoplast, but pass 

 out from a large portion of its surface. At this stage the blepharo- 

 plast may reach a diameter of o. 75 ^ 



In the nucleus are now seen indications of the approaching 

 mitosis which is to differentiate the spermatids. The nuclear 

 reticulum gradually becomes coarser and eventually resolves itself 

 into a spirem (fig. 14). While the spirem is segmenting to form the 

 chromosomes the nuclear membrane breaks down and the fibers 

 radiating from the blepharoplasts extend into the nuclear cavity 

 and establish the karyokinetic figure. The spindle is extremely 



